Express.js Open Redirect in malformed URLs
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 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.
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
Affected software
Click a technology to see all vulnerabilities affecting it.
| Platform | Package | Vulnerable versions | Fixed in |
|---|---|---|---|
| npm package | express | < 4.19.2, >= 5.0.0-alpha.1, < 5.0.0-beta.3 | 4.19.2, 5.0.0-beta.3 |
References
- https://github.com/expressjs/express/security/advisories/GHSA-rv95-896h-c2vc
- https://nvd.nist.gov/vuln/detail/CVE-2024-29041
- https://github.com/koajs/koa/issues/1800
- https://github.com/expressjs/express/pull/5539
- https://github.com/expressjs/express/commit/0867302ddbde0e9463d0564fea5861feb708c2dd
- https://github.com/expressjs/express/commit/0b746953c4bd8e377123527db11f9cd866e39f94
- https://expressjs.com/en/4x/api.html#res.location
- https://github.com/expressjs/express
- CVSS vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N- Weakness (CWE)
CWE-1286, CWE-601- Platform
- npm
- Package
express- Disclosed
- 25.03.2024
- Updated
- 11.10.2026 10:22
Sources and licenses
OSV / GitHub Advisory Database - GHSA-rv95-896h-c2vc - CC BY 4.0
Vulnerability history: express
All published vulnerabilities of this package (npm package), newest first. Shows whether this is a one-off slip or a package that needs watching.
- Total entries
- 5
- First → latest
- 10.2018 10.2024
- Without a fix
- 0
- Exploited in attacks
- 0
Severity breakdown
- Medium 3
- Low 2
Disclosures per year
- 2018: 1
- 2019: 0
- 2020: 0
- 2021: 0
- 2022: 0
- 2023: 0
- 2024: 4
- 2025: 0
- 2026: 0
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Express.js Open Redirect in malformed URLs this entry
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