CVE-2026-126076 Action Pack: Possible restoration of destroyed sessions in Action Dispatch CacheStore

What is CVE-2026-126076?

CVE-2026-126076 is a medium-severity vulnerability in rails, published on 10 Nov 2026.

Official description

Action Pack is a framework for handling and responding to web requests. Prior to 8.1.4.1 and 8.0.5.2, ActionDispatch::Session::CacheStore writes a session back to the cache at the end of each request that loaded it, without checking that the session's cache entry still exists. When a concurrent request destroys the session, through reset_session on logout or by deleting its cache entry on the server, a request that loaded the session earlier and finishes later restores it under its original session ID. Logout and server-side revocation could therefore fail to end a session, and an attacker who holds a stolen session cookie could keep that session valid across the victim's logout. Applications that use config.session_store :cache_store are affected, with any cache backend. ActionDispatch::Session::CookieStore is not affected, nor is ActionDispatch::Session::MemCacheStore with Dalli 4.0.0 or later, whose session store does not write back a session that was deleted. This issue is fixed in versions 8.1.4.1 and 8.0.5.2.

Weakness: CWE-613

Which versions are affected by CVE-2026-126076?

2 open source packages ship an affected version, including actionpack.

How do I fix CVE-2026-126076?

Upgrade actionpack to a fixed version for your release line: 8.0.5.2 or 8.1.4.1.

Is CVE-2026-126076 being exploited?

There is no known exploitation of CVE-2026-126076 in the wild and no public exploit code.

Sources

• CVE record
• NVD
• OSV
• GitHub advisory
• How this page is made

Also known as DEBIAN-CVE-2026-126076, GHSA-2586-8ghr-69fj, UBUNTU-CVE-2026-126076.