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Low, CVSS 3.1amended

Action Pack: Missing SameSite attribute on session cookies from Action Pack session stores

CVE-2026-126067GHSA-gmj8-hvj3-49mw

What to do

Vendor fix available. Upgrade each affected package to the fixed version on its release line (actionpack 8.1.4.1, 8.0.5.2), redeploy, then verify what is actually installed.

This page has no inventory attached, so it cannot say whether you are affected. A vendor fix is not proof that your deployment is fixed.

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Affected packages

  • RubyGems actionpack

    Affected
    >= 8.1.0.beta1, < 8.1.4.1< 8.0.5.2
    Fixed in
    8.0.5.2, 8.1.4.1

Sources

Severity and exploitation
Exploitation
No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.
CVSS
3.1 · CVSS:3.0/AV:N/AC:H/PR:N/UI:R/S:U/C:N/I:L/A:N
EPSS
No dated EPSS signal available.
Source description

As published by the source; long descriptions are shortened.

Impact Action Pack session stores other than `ActionDispatch::Session::CookieStore` (`CacheStore`, `MemCacheStore`, and third-party stores built on `AbstractStore`, `AbstractSecureStore` or the session mixins) write the session cookie without a `SameSite` attribute, regardless of `config.action_dispatch.cookies_same_site_protection`, which defaults to `:lax`. Only `CookieStore` applies the configured policy. In browsers that do not treat a cookie without the attribute as `SameSite=Lax`, a cross-site request could carry the session cookie, possibly leading to cross-site request forgery against actions that do not verify an authenticity token, such as those of API-only applications. Applications are affected when they use a session store other than `CookieStore` and do not pass `same_site:` to `config.session_store`.

Details In the fixed releases, every session store sets the session cookie's `SameSite` attribute from `cookies_same_site_protection` when its options have no…

Dates and revisions
Published by the source
Last modified by the source
Source last checked
  1. Revision 2 · amended ·

    Amended from osv record GHSA-gmj8-hvj3-49mw

  2. Revision 1 · created ·

    Published from ghsa record GHSA-gmj8-hvj3-49mw

Agent brief

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# Patch Next advisory brief: CVE-2026-126067

Advisory: Action Pack: Missing SameSite attribute on session cookies from Action Pack session stores
IDs: CVE-2026-126067, GHSA-gmj8-hvj3-49mw
Record: https://patchnext.com/advisories/cve-2026-126067 (revision 2, source checked 11 Nov 2026, 07:35 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: Low (CVSS 3.1)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: actionpack 8.1.4.1, 8.0.5.2. A vendor fix does not mean a deployment is fixed.

## Affected components
- RubyGems actionpack: affected >= 8.1.0.beta1, < 8.1.4.1; < 8.0.5.2; fixed in 8.0.5.2, 8.1.4.1

## Suggested inspection (read-only)
- RubyGems actionpack: check the installed version with your package manager.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on actionpack.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://github.com/advisories/GHSA-gmj8-hvj3-49mw (GitHub-reviewed advisory GHSA-gmj8-hvj3-49mw lists affected ranges: RubyGems actionpack >=8.1.0.beta1 =0 <8.0.5.2)
- Verified: https://osv.dev/vulnerability/GHSA-gmj8-hvj3-49mw (OSV record GHSA-gmj8-hvj3-49mw lists affected ranges: RubyGems actionpack >=8.1.0.beta1 =0 <8.0.5.2 (fixed))

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