Express.js Open Redirect in malformed URLs
13Vexday Risk Score
No sign of exploitation. No public exploitation artifact known so far.
ssvc Trackcvss 6.1epss 0.8%
exploitation probability
0.8%top 47% of all CVEs
observed exploitation
nono source reports it
In short
Express.js versions before 4.19.2 have a flaw where malformed URLs can bypass redirect security filters, allowing attackers to redirect users to unintended external websites.
Technical detail
CWE-1286/CWE-601 open redirect vulnerability in Express.js res.location() and res.redirect() methods. Malformed URLs are processed by encodeurl in a way that bypasses allow list validation, enabling attackers to redirect authenticated users to attacker-controlled domains when the application accepts user-supplied redirect URLs.
Summary generated and translated by AI from the official description.
Express.js minimalist web framework for node. Versions of Express.js prior to 4.19.0 and all pre-release alpha and beta versions of 5.0 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`](https://github.com/pillarjs/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()`. The vulnerability is fixed in 4.19.2 and 5.0.0-beta.3.
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N
Affected products
expressjs · expressReferences
https://expressjs.com/en/4x/api.html#res.locationhttps://github.com/expressjs/express/commit/0867302ddbde0e9463d0564fea5861feb708c2ddhttps://github.com/expressjs/express/commit/0b746953c4bd8e377123527db11f9cd866e39f94https://github.com/expressjs/express/pull/5539https://github.com/expressjs/express/security/advisories/GHSA-rv95-896h-c2vchttps://github.com/koajs/koa/issues/1800