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
Published · last modified .
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.
EPSS exploit prediction
EPSS: 0.010 (62.1th percentile), scored .
Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 62nd percentile — 62.1% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.
EPSS over last 30 days · oldest: 0.010 · newest: 0.010 · change: 0.000
Affected products
Weakness classification (CWE)
References
- GitHub Issue #1888 (issue-tracking)
- Proposed fix PR #1889 (unmerged) (issue-tracking, patch)
- CommentsWidget::run() at 1.0.0 (technical-description)
- AJAX display controller at 1.0.0 (technical-description)
- Default comments permissions at 1.0.0 (technical-description)
- github.com/Cotonti/Cotonti (product)
- VulnCheck Advisory: Cotonti 1.0.0 Comments Plugin PHP Object Injection via ci Parameter (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.