Summary
Express.js Open Redirect in malformed URLs
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
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().
Untrusted input controls a URL used for redirection, which can forward users to attacker-controlled sites. Typical impact: phishing and credential harvesting via a trusted domain.
CVE-2024-29041 has a CVSS score of 6.1 (Medium). The vector is network-reachable, no privileges required, and user interaction required. A CVSS score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether this affects your application depends on whether the vulnerable code is present and reachable in your environment. A fixed version is available (4.19.2, 5.0.0-beta.3); upgrading removes the vulnerable code path.
Affected versions
Security releases
Kodem intelligence
Severity tells you how bad this could be in the worst case. It does not tell you whether you are exposed. Exploitability and impact are functions of runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A vulnerable package can sit in your dependency tree and never run.
Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter. Kodem's runtime-powered SCA identifies whether this CVE is reachable in your applications.
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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.
Frequently Asked Questions
- What is CVE-2024-29041? CVE-2024-29041 is a medium-severity open redirect vulnerability in express (npm), affecting versions < 4.19.2. It is fixed in 4.19.2, 5.0.0-beta.3. Untrusted input controls a URL used for redirection, which can forward users to attacker-controlled sites.
- How severe is CVE-2024-29041? CVE-2024-29041 has a CVSS score of 6.1 (Medium). This score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether it represents real risk in your environment depends on whether the vulnerable code is present and reachable.
- Which versions of express are affected by CVE-2024-29041? express (npm) versions < 4.19.2 is affected.
- Is there a fix for CVE-2024-29041? Yes. CVE-2024-29041 is fixed in 4.19.2, 5.0.0-beta.3. Upgrade to this version or later.
- Is CVE-2024-29041 exploitable, and should I be worried? Whether CVE-2024-29041 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
- What actually determines whether CVE-2024-29041 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
- How do I fix CVE-2024-29041?
- Upgrade
expressto 4.19.2 or later - Upgrade
expressto 5.0.0-beta.3 or later
- Upgrade