Cotonti CMS's Comments plugin deserializes user-supplied data without restricting the classes that may be instantiated. In plugins/comments/controllers/actions/CreateAction.php, a `ci` POST parameter obtained via `cot_import('ci', 'P', 'TXT')` (trim-only sanitization) is passed to `unserialize(base64_decode($ci))` with no `allowed_classes` restriction, reachable by any member with write access to comments (the default `Auth_members => 'RW'` setting in plugins/comments/comments.setup.php). In plugins/comments/controllers/actions/EditAction.php, a `cb` parameter is similarly deserialized via `unserialize(base64_decode($this->comeback))` in prepareComeBack(), reachable by any member editing their own comment. Because unserialize() is called without allowed_classes, an attacker can construct a serialized PHP object of any class loaded by Cotonti (a PHP Object Injection primitive). This was demonstrated in practice using Cotonti's own MySQL_cache class: a crafted serialized MySQL_cache object, once deserialized and later garbage-collected, triggers its __destruct()->flush() chain, causing an attacker-controlled INSERT INTO cot_cache with attacker-chosen row values — confirming genuine POP-chain exploitation, with further impact (including potential RCE) contingent on other gadget chains available in a given Cotonti installation's loaded classes. A third sink in DeleteAction.php contains the identical unserialize() pattern but is gated behind an admin-only authorization check and is not reachable by ordinary members.

Cotonti CMS's Comments plugin deserializes user-supplied data without restricting the classes that may be instantiated. In plugins/comments/controllers/actions/CreateAction.php, a POST parameter obtained via (trim-only sanitization) is passed to with no restriction, reachable by any member with write access to comments (the default setting in plugins/comments/comments.setup.php).

{"timestamp":"2026-08-05T15:35:00.816320Z","id":"CVE-2026-71294","options":[{"exploitation":"none"},{"automatable":"no"},{"technicalImpact":"partial"}],"role":"CISA Coordinator","version":"2.0.3"}

Cotonti CMS's Comments plugin deserializes user-supplied data without restricting the classes that may be instantiated. In plugins/comments/controllers/actions/CreateAction.php, a `ci` POST parameter obtained via `cot_import('ci', 'P', 'TXT')` (trim-only sanitization) is passed to `unserialize(base64_decode($ci))` with no `allowed_classes` restriction, reachable by any member with write access to comments (the default `Auth_members => 'RW'` setting in plugins/comments/comments.setup.php). In plugins/comments/controllers/actions/EditAction.php, a `cb` parameter is similarly deserialized via `unserialize(base64_decode($this->comeback))` in prepareComeBack(), reachable by any member editing their own comment. Because unserialize() is called without allowed_classes, an attacker can construct a serialized PHP object of any class loaded by Cotonti (a PHP Object Injection primitive). This was demonstrated in practice using Cotonti's own MySQL_cache class: a crafted serialized MySQL_cache object, once deserialized and later garbage-collected, triggers its __destruct()->flush() chain, causing an attacker-controlled INSERT INTO cot_cache with attacker-chosen row values — confirming genuine POP-chain exploitation, with further impact (including potential RCE) contingent on other gadget chains available in a given Cotonti installation's loaded classes. A third sink in DeleteAction.php contains the identical unserialize() pattern but is gated behind an admin-only authorization check and is not reachable by ordinary members.

AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:L/A:L

CWE-502

https://github.com/Cotonti/Cotonti

https://github.com/Cotonti/Cotonti/blob/master/plugins/comments/controllers/actions/CreateAction.php

[{"vendor":"Cotonti","product":"Cotonti","defaultStatus":"unaffected","programFiles":["plugins/comments/controllers/actions/CreateAction.php","plugins/comments/controllers/actions/EditAction.php"],"versions":[{"version":"0","lessThanOrEqual":"*","versionType":"custom","status":"affected"}]}]