nosurf vulnerable to CSRF due to non-functional same-origin request checks
Date: 2025-05
Affected: go/github.com/justinas/nosurf
Attack vector: xss
Category: vulnerability-disclosure
Severity: Medium
CVE: CVE-2025-46721
CWE: CWE-352

### Impact This vulnerability allows an attacker who controls content on the target site, or on a subdomain of the target site (either via XSS, or otherwise) to bypass Cross-Site Request Forgery checks and issue requests on user's behalf. ### Details Due to misuse of the Go `net/http` library, nosurf categorizes all incoming requests as plain-text HTTP requests, in which case the `Referer` header is not checked to have the same origin as the target webpage. If the attacker has control over HTML contents on either the target website (e.g. `example.com`), or on a website hosted on a subdomain of the target (e.g. `attacker.example.com`), they will also be able to manipulate cookies set for the target website. By acquiring the secret CSRF token from the cookie, or overriding the cookie with a new token known to the attacker, `attacker.example.com` is able to craft cross-site requests to `example.com`. ### Patches A patch for the issue was released in nosurf 1.2.0. ### Workarounds In lieu of upgrading to a patched version of nosurf, users may additionally use another HTTP middleware to ensure that a non-safe HTTP request is coming from the same origin (e.g. by requiring a `Sec-Fetch-Site: same-origin` header in the request). ### References https://github.com/advisories/GHSA-rq77-p4h8-4crw https://github.com/justinas/nosurf-cve-2025-46721 https://www.cve.org/CVERecord?id=CVE-2025-46721 https://github.com/justinas/nosurf/releases/tag/v1.2.0


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