The vulnerability arises from an unprotected ZeroMQ PULL socket exposed on a routable network interface by SGLang’s expert-parallel backup subsystem. Because the socket accepts arbitrary Python pickle data without authentication or deserialization safeguards, an attacker can supply a malicious pickle payload that triggers Remote Code Execution on the host. This flaw is a classic example of Deserialization of Untrusted Data (CWE-502) and compromises the confidentiality, integrity, and availability of the affected system.

The affected product is SGLang, specifically the expert-parallel backup subsystem component that communicates over ZeroMQ. No version information is provided; the vulnerability is present whenever the feature is enabled and the service is reachable over the network.

The CVSS base score of 9.1 indicates a high severity vulnerability. The EPSS score is < 1%, indicating a very low but non‑zero exploitation probability. The lack of authentication and network reachability make exploitation likely from any host with network access to the exposed socket. The vulnerability is not listed in CISA KEV, yet the potential for unauthenticated remote code execution means it should be treated as a critical risk. Attackers can exploit this by simply connecting to the ZeroMQ endpoint and sending a crafted pickle over the network.