Cotonti 1.0.0 passes the base64-decoded cb parameter to unserialize() without allowed_classes restriction in the comments plugin EditAction. Registered users with comment write permissions can instantiate arbitrary PHP objects and potentially achieve file write or code execution through gadget chains.
https://github.com/Cotonti/Cotonti/pull/1897
https://github.com/Cotonti/Cotonti/issues/1894
https://github.com/Cotonti/Cotonti/blob/1.0.0/system/cache.php
https://github.com/Cotonti/Cotonti/blob/1.0.0/plugins/comments/controllers/actions/EditAction.php
Published: 2026-09-18
Updated: 2026-09-18
Base Score: 7.1
Vector: CVSS2#AV:N/AC:H/Au:S/C:C/I:C/A:C
Severity: High
Base Score: 7.5
Vector: CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H
Severity: High
Base Score: 7.7
Vector: CVSS:4.0/AV:N/AC:H/AT:P/PR:L/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N
Severity: High
EPSS: 0.00439