The vulnerability allows an attacker to exploit an insecure deserialization bug on the kotaemon check_connection endpoint by supplying crafted YAML or JSON payloads containing a special __type__ field. By forcing the application to instantiate arbitrary Python classes, an attacker can overwrite the __type__ with subprocess.check_output and supply malicious arguments, thereby executing arbitrary code with the privileges of the kotaemon process.

The flaw affects all public releases of the kotaemon application up to and including version 0.12.0. Known affected versions include the full set of releases described by the CPE entries, which are #0.0.0 through #0.4.9. This applies to any installation of Cinnamon:kotaemon that has the check_connection endpoint enabled and reachable over the network.

The CVSS score is 9.3, indicating a high‑severity remote code execution risk. No EPSS score is available, and the vulnerability is not listed in the CISA KEV catalog, but the lack of exploitation data does not diminish the potential impact. Attackers can reach the vulnerable endpoint without authentication, and the bug allows immediate code execution with application process privileges. The chain of exploitation is straightforward: send a crafted request, trigger deserialization, and run arbitrary commands.