CVE-2026-91939: Cotonti 1.0.0 Comments Plugin PHP Object Injection via ci Parameter

Severity: critical (CVSS 9.8 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 1.0% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2026-09-15 · updated 2026-09-16
Weakness: CWE-502

Description

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.

Affected products

Cotonti: from 1.0.0 through 1.0.0

References

https://github.com/Cotonti/Cotonti
https://github.com/Cotonti/Cotonti/blob/1.0.0/plugins/comments/comments.setup.php
https://github.com/Cotonti/Cotonti/blob/1.0.0/plugins/comments/controllers/actions/DisplayAction.php
https://github.com/Cotonti/Cotonti/blob/1.0.0/plugins/comments/inc/CommentsWidget.php
https://github.com/Cotonti/Cotonti/issues/1888
https://github.com/Cotonti/Cotonti/pull/1889
https://www.vulncheck.com/advisories/cotonti-1.0.0-comments-plugin-php-object-injection-via-ci-parameter
https://github.com/Cotonti/Cotonti/issues/1888

Get alerted when CVE-2026-91939 or the next vulnerability affects your stack