CVE-2025-57821: basecamp google_sign_in Open Redirect

Vulnerability summary

CVE-2025-57821 is a medium (CVSS 4.2) Open Redirect vulnerability in basecamp google_sign_in. EPSS estimates a 0.24% chance of exploitation in the next 30 days, higher than 14.2% of scored vulnerabilities.

Timeline

1. 27-08-2025
   PublishedVulnerability first disclosed.
2. 27-08-2025
   Last modifiedVulnerability information updated.

Description

Basecamp's Google Sign-In adds Google sign-in to Rails applications. Prior to version 1.3.0, it is possible to craft a malformed URL that passes the "same origin" check, resulting in the user being redirected to another origin. Rails applications configured to store the flash information in a session cookie may be vulnerable, if this can be chained with an attack that allows injection of arbitrary data into the session cookie. This issue has been patched in version 1.3.0. If upgrading is not possible at this time, a way to mitigate the chained attack can be done by explicitly setting SameSite=Lax or SameSite=Strict on the application session cookie.

• CWE-601URL 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.