Express 4.17.2 represents a subtle but important update over version 4.17.1, offering refinements that benefit developers seeking a stable and reliable Node.js web framework. Examining the dependency changes reveals a focus on security and bug fixes in underlying packages. Key dependencies like qs which moved from version 6.7.0 to 6.9.6, often involve improvements in query string parsing, potentially addressing security vulnerabilities or edge cases. send updated from 0.17.1 to 0.17.2, likely包含修复和小的增强，可以提高文件服务器效率. proxy-addr has been updated from ~2.0.5 to ~2.0.7 fixing proxy address detection. Body-parser moved from 1.19.0 to 1.19.1, which can contain security enhancement or bug fixes, improving the way the app parses data. safe-buffer updated from version 5.1.2 to 5.2.1, an important update due to this package handling buffer allocation, fixing vulnerabilities and improving security. setprototypeof has been updated from 1.1.1 to 1.2.0. content-disposition updated from 0.5.3 to 0.5.4 with probably bug fixes or security updates. Examining the devDependencies shows less important updates for a developer but eslint went from version "2.13.1" to "7.32.0", marked from "0.6.2" to "0.7.0", supertest from "3.3.0" to "6.1.6", connect-redis from "3.4.1" to "3.4.2", cookie-parser from "~1.4.4" to "1.4.6", express-session from "1.16.1" to "1.17.2". Overall, the move from 4.17.1 to 4.17.2 prioritized stability and incremental improvements, making it a recommended upgrade for existing Express users.
All the vulnerabilities related to the version 4.17.2 of the package
Express.js Open Redirect in malformed URLs
Versions of Express.js prior to 4.19.2 and pre-release alpha and beta versions before 5.0.0-beta.3 are affected by an open redirect vulnerability using malformed URLs.
When a user of Express performs a redirect using a user-provided URL Express performs an encode using encodeurl on the contents before passing it to the location header. This can cause malformed URLs to be evaluated in unexpected ways by common redirect allow list implementations in Express applications, leading to an Open Redirect via bypass of a properly implemented allow list.
The main method impacted is res.location() but this is also called from within res.redirect().
https://github.com/expressjs/express/commit/0867302ddbde0e9463d0564fea5861feb708c2dd https://github.com/expressjs/express/commit/0b746953c4bd8e377123527db11f9cd866e39f94
An initial fix went out with express@4.19.0, we then patched a feature regression in 4.19.1 and added improved handling for the bypass in 4.19.2.
The fix for this involves pre-parsing the url string with either require('node:url').parse or new URL. These are steps you can take on your own before passing the user input string to res.location or res.redirect.
https://github.com/expressjs/express/pull/5539 https://github.com/koajs/koa/issues/1800 https://expressjs.com/en/4x/api.html#res.location
express vulnerable to XSS via response.redirect()
In express <4.20.0, passing untrusted user input - even after sanitizing it - to response.redirect() may execute untrusted code
this issue is patched in express 4.20.0
users are encouraged to upgrade to the patched version of express, but otherwise can workaround this issue by making sure any untrusted inputs are safe, ideally by validating them against an explicit allowlist
successful exploitation of this vector requires the following:
qs vulnerable to Prototype Pollution
qs before 6.10.3 allows attackers to cause a Node process hang because an __ proto__ key can be used. In many typical web framework use cases, an unauthenticated remote attacker can place the attack payload in the query string of the URL that is used to visit the application, such as a[__proto__]=b&a[__proto__]&a[length]=100000000. The fix was backported to qs 6.9.7, 6.8.3, 6.7.3, 6.6.1, 6.5.3, 6.4.1, 6.3.3, and 6.2.4.
send vulnerable to template injection that can lead to XSS
passing untrusted user input - even after sanitizing it - to SendStream.redirect() may execute untrusted code
this issue is patched in send 0.19.0
users are encouraged to upgrade to the patched version of express, but otherwise can workaround this issue by making sure any untrusted inputs are safe, ideally by validating them against an explicit allowlist
successful exploitation of this vector requires the following:
cookie accepts cookie name, path, and domain with out of bounds characters
The cookie name could be used to set other fields of the cookie, resulting in an unexpected cookie value. For example, serialize("userName=<script>alert('XSS3')</script>; Max-Age=2592000; a", value) would result in "userName=<script>alert('XSS3')</script>; Max-Age=2592000; a=test", setting userName cookie to <script> and ignoring value.
A similar escape can be used for path and domain, which could be abused to alter other fields of the cookie.
Upgrade to 0.7.0, which updates the validation for name, path, and domain.
Avoid passing untrusted or arbitrary values for these fields, ensure they are set by the application instead of user input.
body-parser vulnerable to denial of service when url encoding is enabled
body-parser <1.20.3 is vulnerable to denial of service when url encoding is enabled. A malicious actor using a specially crafted payload could flood the server with a large number of requests, resulting in denial of service.
this issue is patched in 1.20.3
serve-static vulnerable to template injection that can lead to XSS
passing untrusted user input - even after sanitizing it - to redirect() may execute untrusted code
this issue is patched in serve-static 1.16.0
users are encouraged to upgrade to the patched version of express, but otherwise can workaround this issue by making sure any untrusted inputs are safe, ideally by validating them against an explicit allowlist
successful exploitation of this vector requires the following:
path-to-regexp outputs backtracking regular expressions
A bad regular expression is generated any time you have two parameters within a single segment, separated by something that is not a period (.). For example, /:a-:b.
For users of 0.1, upgrade to 0.1.10. All other users should upgrade to 8.0.0.
These versions add backtrack protection when a custom regex pattern is not provided:
They do not protect against vulnerable user supplied capture groups. Protecting against explicit user patterns is out of scope for old versions and not considered a vulnerability.
Version 7.1.0 can enable strict: true and get an error when the regular expression might be bad.
Version 8.0.0 removes the features that can cause a ReDoS.
All versions can be patched by providing a custom regular expression for parameters after the first in a single segment. As long as the custom regular expression does not match the text before the parameter, you will be safe. For example, change /:a-:b to /:a-:b([^-/]+).
If paths cannot be rewritten and versions cannot be upgraded, another alternative is to limit the URL length. For example, halving the attack string improves performance by 4x faster.
Using /:a-:b will produce the regular expression /^\/([^\/]+?)-([^\/]+?)\/?$/. This can be exploited by a path such as /a${'-a'.repeat(8_000)}/a. OWASP has a good example of why this occurs, but the TL;DR is the /a at the end ensures this route would never match but due to naive backtracking it will still attempt every combination of the :a-:b on the repeated 8,000 -a.
Because JavaScript is single threaded and regex matching runs on the main thread, poor performance will block the event loop and can lead to a DoS. In local benchmarks, exploiting the unsafe regex will result in performance that is over 1000x worse than the safe regex. In a more realistic environment using Express v4 and 10 concurrent connections, this translated to average latency of ~600ms vs 1ms.
path-to-regexp contains a ReDoS
The regular expression that is vulnerable to backtracking can be generated in versions before 0.1.12 of path-to-regexp, originally reported in CVE-2024-45296
Upgrade to 0.1.12.
Avoid using two parameters within a single path segment, when the separator is not . (e.g. no /:a-:b). Alternatively, you can define the regex used for both parameters and ensure they do not overlap to allow backtracking.
