A vulnerability, which was classified as critical, was found in TemmokuMVC up to 2.3. Affected is the function get_img_url/img_replace in the library lib/images_get_down.php of the component Image Download Handler. The manipulation leads to deserialization. It is possible to launch the attack remotely. The complexity of an attack is rather high. The exploitability is told to be difficult. The exploit has been disclosed to the public and may be used. The identifier of this vulnerability is VDB-254532. NOTE: The vendor was contacted early about this disclosure but did not respond in any way.
The product deserializes untrusted data without sufficiently verifying that the resulting data will be valid.
It is often convenient to serialize objects for communication or to save them for later use. However, deserialized data or code can often be modified without using the provided accessor functions if it does not use cryptography to protect itself. Furthermore, any cryptography would still be client-side security – which is a dangerous security assumption. Data that is untrusted can not be trusted to be well-formed. When developers place no restrictions on “gadget chains,” or series of instances and method invocations that can self-execute during the deserialization process (i.e., before the object is returned to the caller), it is sometimes possible for attackers to leverage them to perform unauthorized actions, like generating a shell.