PatchTheCVECVE-2026-91939: Cotonti 1.0.0 Comments plugin passes the ci GET parameter to unserialize() without allowed_classes restriction
CVE-2026-91939 is a critical-severity flaw (CVSS 9.8) affecting affected software. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.
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.
Why this priority
- Critical severity
- CISA SSVC: public proof of concept
- CISA SSVC: automatable with total technical impact
- Remotely exploitable, no login, no user action
A fixed release or distro patch exists.
Risk facts
| CVSS score | 9.8 (Critical) |
| Attack vector | Network (remote) |
| Attack complexity | Low |
| Privileges needed | None |
| User interaction | None |
| EPSS exploit chance | 1.0% (top 38%) |
| CISA exploited list | No |
| Weakness | CWE-502 |
| Published | 2026-09-15 |
| Last modified | 2026-09-16 |
Last updated 2026-09-16 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score
Timeline
- Published CVE record published
- Updated Record last modified
Exact fixes by distribution
Public exploits and detection
Public code exists for this CVE. Treat unpatched systems as at risk, and only run PoCs in a lab.
- Write-up: github.com/Cotonti/Cotonti/issues/1888
Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.
Quick answers
How do I fix CVE-2026-91939?
No fixed release is listed yet. Watch the vendor advisory and apply any mitigation shown on this page.
Is CVE-2026-91939 being exploited?
CVE-2026-91939 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.
What does CVE-2026-91939 affect?
CVE-2026-91939 affects affected software. Severity is critical (CVSS 9.8). 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 explo
How urgent is CVE-2026-91939?
Priority 61/100. Critical severity; CISA SSVC: public proof of concept; CISA SSVC: automatable with total technical impact; Remotely exploitable, no login, no user action