Deserialization in Cotonti
CVE-2026-91939
Cotonti 1.0.0 Comments plugin passes the ci GET parameter to unserialize() without allowed_classes restriction, allowing unauthenticated attackers to instantiate arbitrary PHP classes with attacker-controlled properties. Attackers can exploit PHP object injection through crafted serialized payloads to trigger gadget chains and achieve database manipulation or code execution.
Vulnerability class: Insecure Deserialization
CVSS v3 metric
CVSS v3 base score 9.8 (Critical). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H.
Affected products
Weakness classification (CWE)
References
- disclosure@vulncheck.com (issue-tracking)
- disclosure@vulncheck.com (issue-tracking, patch)
- disclosure@vulncheck.com (technical-description)
- disclosure@vulncheck.com (technical-description)
- disclosure@vulncheck.com (technical-description)
- disclosure@vulncheck.com (product)
- disclosure@vulncheck.com (third-party-advisory)
Frequently asked questions
- What is CVE-2026-91939?
- CVE-2026-91939 is a critical-severity vulnerability in Cotonti, classified under Deserialization of Untrusted Data. CVSS score: 9.8/10. Published 2026-09-15.
- How severe is CVE-2026-91939?
- Critical severity. CVSS v3 base score is 9.8 out of 10.