CVE-2026-126077
Received
Received - Intake
Session Fixation in Action Pack via Active Storage Cache
Vulnerability report for CVE-2026-126077, including description, CVSS score, EPSS score, affected products, exploitability, helpful resources, and attack-flow context.
Publication date: 2026-11-10
Last updated on: 2026-11-10
Assigner: GitHub, Inc.
Description
Description
Action Pack is a framework for handling and responding to web requests. Prior to 8.1.4.1 and 8.0.5.2, When ActionDispatch::Cookies reads a signed or encrypted cookie that was written under a rotated secret (config.action_dispatch.cookies_rotations) or in the format that a :hybrid cookie serializer migrates from, it writes the cookie back to the response in the current format, and that write ignores request.session_options[:skip]. ActiveStorage::DisableSession relies on that option to keep the session cookie off the public, immutable responses of the Active Storage proxy controllers, but those controllers still load the session, so a request carrying an old-format session cookie could receive the rewritten session cookie in Set-Cookie on a cacheable response. A shared cache that stores such a response together with its Set-Cookie header could then serve one user's session to later requesters of the same URL, or serve an attacker's session to other users. Applications are affected when they serve Active Storage files through the proxy controllers, have a cookie rotation or a :hybrid serializer migration configured, and run behind a cache that stores Set-Cookie on public responses. This is a path around the fix for CVE-2024-26144. This issue is fixed in versions 8.1.4.1 and 8.0.5.2.
CVSS Scores
EPSS Scores
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| Percentile: |
Meta Information
Affected Vendors & Products
| Vendor | Product | Version / Range |
|---|---|---|
| rubyonrails | action_pack | to 8.0.5.2 (exc) |
| rubyonrails | activestorage | to 8.0.5.2 (exc) |
Helpful Resources
Exploitability
CWE
KEV
| CWE ID | Description |
|---|---|
| CWE-200 | The product exposes sensitive information to an actor that is not explicitly authorized to have access to that information. |
