What’s Vulnerable › Vulnerabilities

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

• Severity: high (CVSS 8.8 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.6% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2026-07-30 · updated 2026-10-23
• Weakness: CWE-304

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

• s9y Serendipity: before 2.6.1 — fixed in 2.6.1

How to fix

Upgrade to a fixed version: s9y Serendipity 2.6.1. Check the vendor advisory for mitigations.

References

• https://github.com/s9y/Serendipity/security/advisories/GHSA-v645-243f-jwgh
• https://www.vulncheck.com/advisories/serendipity-authentication-bypass-via-username-collision
• https://github.com/s9y/Serendipity/security/advisories/GHSA-v645-243f-jwgh

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