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Vulnerability record · CVE-2026-91939 · published 15 September 2026

CVE-2026-91939: Deserialization of untrusted data vulnerability

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.

9.3 CVSS 4.0 Critical EPSS 0.98% · top 39.3% CWE-502 · Deserialization of untrusted data Deferred
9.3CVSS 4.0 base score
0.98%EPSS exploitation probability, 30 days
NoNot in CISA KEV
0Affected product versions listed by NVD
8References
16 Sep 2026Last modified by NVD

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.

CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:

References

LinkTags
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

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Source: NIST National Vulnerability Database (record CVE-2026-91939), CISA KEV, FIRST EPSS (scores of 2026-09-26). This page is refreshed as NVD updates the record.