GHSA-rv95-896h-c2vc CVE-2024-29041
Express.js Open Redirect in malformed URLs
- Severity
- 6.1 / 10
- Medium · CVSS 3.1
- Exploit chance (EPSS)
- 0.79%
- Chance of exploitation in the next 30 days. Higher than 56.13% of scored vulnerabilities.
- Known exploited
- No
- Not in CISA's catalog
- Weakness
- CWE-601 URL Redirection to Untrusted Site ('Open Redirect')
- CWE-1286 Improper Validation of Syntactic Correctness of Input
- Fix
4.19.2- Upgrade express to this version or later
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 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 versions
npm
| Package | Vulnerable | Fixed in |
|---|---|---|
| express | < 4.19.2 |
4.19.2 |
| express | >= 5.0.0-alpha.1, < 5.0.0-beta.3 |
5.0.0-beta.3 |
| express | < 4.19.2 |
4.19.2 |
| express | >= 5.0.0-alpha.1, < 5.0.0-beta.3 |
5.0.0-beta.3 |
How to fix
Move to the fixed version or later with your package manager, update the lockfile, and run your tests. If the package only arrives through another dependency, upgrade that dependency first. If none of its releases pulls a fixed version yet, force the version with your package manager's override.
express npm → 4.19.2
- npm
npm install express@4.19.2- yarn
yarn add express@4.19.2- pnpm
pnpm add express@4.19.2
Severity breakdown
CVSS 3.1 6.1
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N
- Attack vector
- Network
- Attack complexity
- Low
- Privileges required
- None
- User interaction
- Required
- Scope
- Changed
- Confidentiality
- Low
- Integrity
- Low
- Availability
- None
Weakness
CWE-601: URL Redirection to Untrusted Site ('Open Redirect')
The web application accepts a user-controlled input that specifies a link to an external site, and uses that link in a redirect.
How to prevent it
- Implementation: Assume all input is malicious. Use an "accept known good" input validation strategy, i.e., use a list of acceptable inputs that strictly conform to specifications. Reject any input that does not strictly conform to specifications, or transform it into something that does. When performing input validation, consider all potentially relevant properties, including length, type of input, the full range of acceptable values, missing or extra inputs, syntax, consistency across related fields, and conformance to business rules. As an example of business rule logic, "boat" may be syntactically valid because it only contains alphanumeric characters, but it is not valid if the input is only expected to contain colors such as "red" or "blue." Do not rely exclusively on looking for malicious or malformed inputs. This is likely to miss at least one undesirable input, especially if the code's environment changes. This can give attackers enough room to bypass the intended validation. However, denylists can be useful for detecting potential attacks or determining which inputs are so malformed that they should be rejected outright. Use a list of approved URLs or domains to be used for redirection.
- Architecture and Design: Use an intermediate disclaimer page that provides the user with a clear warning that they are leaving the current site. Implement a long timeout before the redirect occurs, or force the user to click on the link. Be careful to avoid XSS problems (CWE-79) when generating the disclaimer page.
- Architecture and Design: When the set of acceptable objects, such as filenames or URLs, is limited or known, create a mapping from a set of fixed input values (such as numeric IDs) to the actual filenames or URLs, and reject all other inputs. For example, ID 1 could map to "/login.asp" and ID 2 could map to "http://www.example.com/". Features such as the ESAPI AccessReferenceMap [REF-45] provide this capability.
- Architecture and Design: Ensure that no externally-supplied requests are honored by requiring that all redirect requests include a unique nonce generated by the application [REF-483]. Be sure that the nonce is not predictable (CWE-330).
- Architecture and Design, Implementation: Understand all the potential areas where untrusted inputs can enter your software: parameters or arguments, cookies, anything read from the network, environment variables, reverse DNS lookups, query results, request headers, URL components, e-mail, files, filenames, databases, and any external systems that provide data to the application. Remember that such inputs may be obtained indirectly through API calls. Many open redirect problems occur because the programmer assumed that certain inputs could not be modified, such as cookies and hidden form fields.
- Operation: Use an application firewall that can detect attacks against this weakness. It can be beneficial in cases in which the code cannot be fixed (because it is controlled by a third party), as an emergency prevention measure while more comprehensive software assurance measures are applied, or to provide defense in depth [REF-1481].
CWE-1286: Improper Validation of Syntactic Correctness of Input
The product receives input that is expected to be well-formed - i.e., to comply with a certain syntax - but it does not validate or incorrectly validates that the input complies with the syntax.
How to prevent it
- Implementation: Assume all input is malicious. Use an "accept known good" input validation strategy, i.e., use a list of acceptable inputs that strictly conform to specifications. Reject any input that does not strictly conform to specifications, or transform it into something that does. When performing input validation, consider all potentially relevant properties, including length, type of input, the full range of acceptable values, missing or extra inputs, syntax, consistency across related fields, and conformance to business rules. As an example of business rule logic, "boat" may be syntactically valid because it only contains alphanumeric characters, but it is not valid if the input is only expected to contain colors such as "red" or "blue." Do not rely exclusively on looking for malicious or malformed inputs. This is likely to miss at least one undesirable input, especially if the code's environment changes. This can give attackers enough room to bypass the intended validation. However, denylists can be useful for detecting potential attacks or determining which inputs are so malformed that they should be rejected outright.
References
Advisories
Fixes and patches
Packages
Other links
Timeline
- Published
- Last updated by the source
- Latest EPSS score
Related advisories
| Advisory | Severity | Why it's related |
|---|---|---|
| GHSA-cm5g-3pgc-8rg4 Express ressource injection | Medium | Also affects express |
| GHSA-jj78-5fmv-mv28 Express Open Redirect vulnerability | Medium | Also affects express |
| GHSA-qw6h-vgh9-j6wx express vulnerable to XSS via response.redirect() | Medium | Also affects express |
| GHSA-gpvr-g6gh-9mc2 No Charset in Content-Type Header in express | Medium | Also affects express |
| GHSA-pfhg-q3qv-9q6r SvelteKit: URL redirection to untrusted site via enhanced form submission | Medium | Same weakness, CWE-601 |
| GHSA-w84c-53h3-mc2g Payload: Untrusted redirect URL parameter exploit | Medium | Same weakness, CWE-601 |
| GHSA-r4gj-5m52-g5wh Axios: maxRedirects: 0 is not enforced by the fetch adapter, allowing redirect-based SSRF | High | Same weakness, CWE-601 |
| EEF-CVE-2026-82731 Unescaped path parameters in AshTypescript generated TypeScript client allow request redirection | Not rated yet | Same weakness, CWE-601 |
Credits: FDrag0n, UlisesGascon, blakeembrey, ctcpip, jonchurch, ruddermann, wesleytodd
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