CVE-2026-71294
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 P
No public exploitation has been reported so far. No distribution fix is listed yet; apply vendor mitigations and monitor.
Recommended action: Track your distribution's security tracker and apply the fix as soon as it ships.
Severity metrics
CVSS 3.1 : 7.6 HIGH
Vector: AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:L/A:L
Affected & fixed versions by distribution
Versions are the native distribution strings (backport-aware): RHEL/Debian/SUSE backport fixes, so compare with the distro version comparator (dpkg / rpm / vercmp), not the upstream version.
No affected package in the tracked watchlist yet (Debian, Ubuntu, Arch, SUSE, Red Hat...). Triage may still be pending.