katalyst-koi: Session cookies can be replayed after user logout

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS

7.4 · CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N

EPSS

• CVE-2026-44511: 0.20% estimated exploitation activity in the next 30 days; percentile 9.51 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.

As published by the source; long descriptions are shortened.

Impact Admin session cookies were not invalidated when an admin user logged out. An attacker with access to a valid admin session cookie could continue to access admin functionality after logout, until the cookie expired or session secrets were rotated. This affects applications using Koi admin authentication where an admin session cookie may have been exposed, cached, intercepted, or otherwise retained after logout. Patches The issue has been patched by recording admin logout time and rejecting any admin session cookie created before the user’s most recent logout. Users should upgrade to the patched Koi releases once available. Workarounds Katalyst Koi recommends upgrading to the latest available version, or back porting the changes released in 5.6.0/4.20.0 Resources This is an application of https://guides.rubyonrails.org/v5.2.0/security.html#replay-attacks-for-cookiestore-sessions

Published by the source

7 May 2026, 02:13 UTC

Last modified by the source

29 May 2026, 21:45 UTC

Source last checked

26 Oct 2026, 15:52 UTC

1. Revision 1 · created · 26 Oct 2026

   Published from ghsa record GHSA-4cx3-3c38-j9vv

Preview the exact text before you copy it. Commands are read-only suggestions; review them before running anything.

# Patch Next advisory brief: CVE-2026-44511

Advisory: katalyst-koi: Session cookies can be replayed after user logout
IDs: CVE-2026-44511, GHSA-4cx3-3c38-j9vv
Record: https://patchnext.com/advisories/cve-2026-44511 (revision 1, source checked 26 Oct 2026, 15:52 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: High (CVSS 7.4)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: katalyst-koi 5.6.0, 4.20.0. A vendor fix does not mean a deployment is fixed.

## Affected components
- RubyGems katalyst-koi: affected < 4.20.0; >= 5.0.0, < 5.6.0; fixed in 5.6.0, 4.20.0

## Suggested inspection (read-only)
- RubyGems katalyst-koi: 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 katalyst-koi.
- 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-4cx3-3c38-j9vv (GitHub-reviewed advisory GHSA-4cx3-3c38-j9vv lists affected ranges: RubyGems katalyst-koi >=0 =5.0.0 <5.6.0)

Commands are suggestions: review each one before running it.