The vulnerability allows an attacker to execute arbitrary Python code on the host. An insecure /exec‑py route in Mesop’s ai testing module accepts base64‑encoded Python code and executes it without authentication or validation, leading to uncontrolled code execution on the server and representing a classic code injection flaw identified as CWE‑94.

The affected product is Mesop from mesop‑dev. Versions 1.2.2 and earlier are impacted; the issue was fixed in 1.2.3.

With a CVSS score of 9.8 the risk is extremely high. The EPSS score is 8%, indicating a higher public exploitation probability, but the vulnerability can be triggered by any unauthenticated HTTP request to the /exec‑py endpoint, which can be accessed by anyone able to route traffic to the Mesop application. The non‑authenticatable route allows immediate host‑level command execution and is not listed in the CISA KEV catalog.