Express.js Open Redirect in malformed URLs

CVE-2024-29041 → View on GitHub ↗ View on CVE.org ↗ View on NVD ↗

Description

Impact

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().

Patches

https://github.com/expressjs/express/commit/0867302ddbde0e9463d0564fea5861feb708c2dd
https://github.com/expressjs/express/commit/0b746953c4bd8e377123527db11f9cd866e39f94

An initial fix went out with [email protected], we then patched a feature regression in 4.19.1 and added improved handling for the bypass in 4.19.2.

Workarounds

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.

Resources

https://github.com/expressjs/express/pull/5539
https://github.com/koajs/koa/issues/1800
https://expressjs.com/en/4x/api.html#res.location

Basic information

Type
reviewed
Severity
medium
Advisory on GitHub
Open advisory ↗
Repository advisory
Open repository advisory ↗
Source code
Browse source ↗
Published (advisory)
2024-03-25 19:40:26 UTC
Updated
2025-12-20 00:09:31 UTC
GitHub reviewed
2024-03-25 19:40:26 UTC
NVD published
2024-03-25

EPSS Score

Score Percentile
0.15% 36.16%

CVSS Scores

Base score Version Severity Vector
6.1 3.1 —
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N Click to expand
Attack vector (AV:N)
Could be attacked over the internet or any normal routed network—not just someone sitting at the machine.
Attack complexity (AC:L)
Once they can reach the bug, pulling it off is straightforward—no weird race conditions or rare setup.
Privileges required (PR:N)
No account or special rights needed—anonymous or random user is enough.
User interaction (UI:R)
A real person has to do something—click, install, enable—otherwise it doesn’t land.
Scope (S:C)
Breaking this can reach past the original component and bite other resources—bigger blast radius.
Confidentiality (C:L)
Some sensitive info could get out, but not a total data dump.
Integrity (I:L)
Attackers could change some data, but it’s limited—not everything goes.
Availability (A:N)
Service keeps running; no real outage angle.

Identifiers

Type Value
GHSA GHSA-rv95-896h-c2vc ↗
CVE CVE-2024-29041 ↗

CWEs

CWE id Name
CWE-601 URL Redirection to Untrusted Site ('Open Redirect')
CWE-1286 Improper Validation of Syntactic Correctness of Input

Credits

  • FDrag0n (reporter)
  • jonchurch (remediation_developer)
  • blakeembrey (remediation_developer)
  • wesleytodd (remediation_developer)
  • ruddermann (coordinator)
  • ctcpip (coordinator)
  • UlisesGascon (analyst)

Affected packages (2)

Vulnerable version ranges and first patched releases as published by GitHub.

Ecosystem Package Vulnerable range First patched Vulnerable functions
npm express < 4.19.2 4.19.2 —
npm express >= 5.0.0-alpha.1, < 5.0.0-beta.3 5.0.0-beta.3 —

References

cvelogic Threat Intelligence