CVE-2026-126076: Ruby on Rails logout bypass in CacheStore

Summary

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.

cve.now Index

24Pcve.now Index 24 of 100 · methodology v3 · provisional

Exploitation?/40Unknown. No CISA SSVC exploitation rating yet
Exposure3/25Reachable over the network · Unknown: No advisory context yet
Reach17/20Affects Ruby on Rails (a widely deployed server, runtime, framework or database)
Severity4.2/10CVSS 4.2
No patch0/5No signal

What would change the score

Would score about 79 if added to CISA KEV
Would score about 74 if CISA's SSVC rates exploitation active
Would score about 43 if advisories confirm default setups are exposed

How the score works · Rankings

What to do

Upgrade to a fixed version: 8.1.4.1, 8.0.5.2.

Check your systems with an agent

Paste this into a coding or ops agent. It checks your systems read-only and reports a table per asset.

Check whether my systems are affected by CVE-2026-126076 (Action Pack: Possible restoration of destroyed sessions in Action Dispatch CacheStore), using the cve.now data below.

Rules: work read-only. Do not run exploit code, proof-of-concept scripts or scanners that send attack payloads, and do not change any configuration, package, image or deployment. Report findings only.

What cve.now has for CVE-2026-126076 (entry last updated 2026-11-10):
Affected:
- rails rails: from 8.1, fixed in 8.1.4.1; fixed in 8.0.5.2
- RubyGems package actionpack: from 8.1.0.beta1, fixed in 8.1.4.1
- RubyGems package actionpack: fixed in 8.0.5.2
Fixed versions: 8.1.4.1, 8.0.5.2.
Setup: unknown whether the bug needs a non-default feature or setting. Check the advisory.
CISA KEV: CVE-2026-126076 is not listed as of cve.now's last read.
This KEV status is for CVE-2026-126076 only. If you also check another CVE, look up its own KEV status; never assume it from this one.

How to check:
- Packages (RubyGems): find every lockfile in each project and run check_stack from the cve.now MCP server on each one. Compare the resolved versions, not the ranges a manifest declares, with the affected versions above. Include transitive dependencies.
- Installed software: check what is actually running, not what a repo declares. Read the version from each host, container image and Kubernetes node (the binary's version output, the OS package database, image layers), and check whether the conditions above hold there. Distribution packages may carry a backported fix under an older version number; confirm against the distribution's own advisory.

Verify against the linked advisories before concluding, and cite the date you read each one:
- https://github.com/rails/rails/security/advisories/GHSA-2586-8ghr-69fj
- https://github.com/rails/rails/commit/5bb5ec66ed8faaf590ffe1222d7a5eb6e9d050f5
- https://github.com/rails/rails/commit/d479192cf88a8b30a335a8bc25188a2d8e0f8d9f
- https://github.com/rails/rails/releases/tag/v8.0.5.2
- https://github.com/rails/rails/releases/tag/v8.1.4.1
Do not conclude an asset is unaffected unless you checked it and the evidence covers both its version and the conditions above. If you could not check something, mark it unknown and say what is missing.

Report a table with one row per asset and these columns: Asset | Version or build | Status (affected, fixed, not applicable, unknown) | Compensating controls | Exposure (internet-facing, internal, none) | Evidence | Next action.

Entry: https://cve.now/CVE-2026-126076
For follow-up questions, use the cve.now MCP server at https://mcp.cve.now/mcp (no authentication), for example get_vulnerability with id CVE-2026-126076.

Timeline

Nov 10, 2026, 8:57 PM UTCCVE published
Nov 10, 2026, 9:26 PM UTCFirst seen by cve.now

Affected versions

rails rails
From 8.1 · fixed in 8.1.4.1; fixed in 8.0.5.2
actionpackRubyGems
From 8.1.0.beta1 · fixed in 8.1.4.1
actionpackRubyGems
fixed in 8.0.5.2

Evidence 7

Vendor advisory · 1

Establishes: Affected and fixed versions.

Advisory
GitHub · rails/rails · Advisory GHSA-2586-8ghr-69fj

CVE record · 2

Establishes: The identifier and description.

Record
CVE List · CVE-2026-126076
Record
NVD · CVE-2026-126076

Corrections

None so far.

Something wrong on this page? Report an error. Every fix is listed here.

Questions about CVE-2026-126076

Is CVE-2026-126076 being exploited?

It is not in CISA's Known Exploited Vulnerabilities catalog, and CISA's SSVC assessment does not mark exploitation as active. That does not mean it has not been attacked: vendors and researchers can report attacks before CISA lists them. No public exploit code is tracked.Source: cve.now feed data

Which versions are affected by CVE-2026-126076?

rails: from 8.1 before 8.1.4.1; before 8.0.5.2. actionpack (RubyGems): from 8.1.0.beta1 before 8.1.4.1. actionpack (RubyGems): before 8.0.5.2.Source: cve.now feed data

How do I fix CVE-2026-126076?

Upgrade to a fixed version: 8.1.4.1, 8.0.5.2.Source: cve.now feed data

Action Pack: Possible restoration of destroyed sessions in Action Dispatch CacheStore