CVE-2026-126067: Action Pack: Missing SameSite attribute on session cookies from Action Pack session stores

CVE-2026-126067 · Severity: low · CVSS 3.1 · Published 2026-11-10

Action Pack is a framework for handling and responding to web requests. Prior to 8.1.4.1 and 8.0.5.2, 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. This issue is fixed in versions 8.1.4.1 and 8.0.5.2.

Technologies: actionpack (RubyGems). Vendors: RubyGems.

Quick answers

Is CVE-2026-126067 exploited in the wild?
No. Junglewise Threat Intelligence has no report of CVE-2026-126067 being exploited in the wild.
How severe is CVE-2026-126067?
Low severity, with a CVSS score of 3.1, published 10 November 2026.
Which products and versions are affected?
actionpack (RubyGems) >= 8.1.0.beta1, < 8.1.4.1, ECOSYSTEM:introduced=8.1.0.beta1,fixed=8.1.4.1.
Is there a fix for CVE-2026-126067?
Yes. actionpack (RubyGems): upgrade to 8.1.4.1 or later. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.
Am I affected by CVE-2026-126067?
Check whether you run actionpack (RubyGems) at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

How to fix

  • actionpack (RubyGems): upgrade to 8.1.4.1 or later
    bundle update actionpack

Affected products

  • actionpack (RubyGems) >= 8.1.0.beta1, < 8.1.4.1, ECOSYSTEM:introduced=8.1.0.beta1,fixed=8.1.4.1

Identifiers

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

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