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GHSA-4cx3-3c38-j9vv

HighCVSS 7.4 / 10
Published May 7, 2026·Last modified May 7, 2026
Affected Components(0)

No affected components available

Description

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

Risk Scores
Base Score
7.4

The vulnerability can be exploited over the network without needing physical access. It is difficult for an attacker to exploit this vulnerability and may require special conditions. An attacker does not need any special privileges or access rights. No user interaction is needed for the attacker to exploit this vulnerability. The impact is confined to the system where the vulnerability exists. There is a high impact on the confidentiality of the information. There is a high impact on the integrity of the data.

Threat Intelligence
6.8

Exploitation attempts have been detected. Elevated vigilance and prompt remediation are advised.

EPSS
0.20%

The exploit probability is very low. The vulnerability is unlikely to be exploited in the next 30 days.

Exploit
Not available

We did not find any exploit available. Neither in GitHub repositories nor in the Exploit-Database.

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