Vulnerability · Published Jul 30, 2026 · Assigned by VulnCheck

CVE-2026-67351Serendipity < 2.6.1 Authentication Bypass via Username Collision

High 8.8

In plain English

A high-severity security flaw in Serendipity from s9y. Proof-of-concept exploit code is public. The chance it is exploited in the next 30 days is estimated at 0.6% (higher than 46% of all known vulnerabilities).

Severity (CVSS 3.1)8.8High

Exploit odds (30 days)0.6%top 53.5% of all CVEs

Exploited in the wildNo reportsCISA SSVC: poc

Attack toolingNoneno public tooling known

Official description

Serendipity before 2.6.1 contains an authentication context confusion vulnerability where password validation and session loading operate independently without ensuring both use the same user record. An authenticated Editor can create a username collision with an Administrator account and obtain administrative privileges by logging in with their own password while the session loads the Administrator's account data.

Affected products (as reported)

Vendor	Product	Versions
s9y	Serendipity	0 – before 2.6.1

Weakness: CWE-304 · Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

References

GitHub Security Advisory (GHSA-v645-243f-jwgh) vendor-advisory
https://www.vulncheck.com/advisories/serendipity-authentication-bypass-via-username-collision third-party-advisory