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


- **Severity:** Medium 4.2 (`CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:L/I:L/A:N`)
- **Exploited in the wild:** Not known
- **Fix available:** Yes
- **Published:** 10 Nov 2026
- **Updated:** 12 Nov 2026
- **Also known as:** DEBIAN-CVE-2026-126076, GHSA-2586-8ghr-69fj, UBUNTU-CVE-2026-126076

## 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 (DEPRECATED: Insufficient Session Expiration)

## Which versions are affected by CVE-2026-126076?

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


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `actionpack` | RubyGems | All versions | 8.0.5.2 |
| `actionpack` | RubyGems | From 8.1.0.beta1 | 8.1.4.1 |

## 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.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-126076 and fix it if it is affected.

What it is: CVE-2026-126076 is a medium-severity vulnerability in rails, published on 10 Nov 2026. 
Exploitation: There is no known exploitation of CVE-2026-126076 in the wild and no public exploit code.

Affected packages and fixed versions:
- actionpack (RubyGems): affected all versions; fixed in 8.0.5.2
- actionpack (RubyGems): affected from 8.1.0.beta1; fixed in 8.1.4.1

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-126076/ (Markdown: https://insights.sbomify.com/CVE-2026-126076/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-126076
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-126076
- OSV: https://osv.dev/vulnerability/CVE-2026-126076

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-126076/
Summaries are generated and may contain mistakes; the official description above is the record.