LMCache remote code execution via unsafe deserialization in multiprocess transport

Severity: critical · CVSS 9.8 · Published 2026-10-07

LMCache is a distributed caching system for large language models that uses multiprocess mode to share data across worker processes. An unauthenticated attacker on the network can send a specially crafted message to the ZeroMQ transport port and execute arbitrary code as the user running LMCache, typically root in container deployments. This grants complete control over the system.

Technologies: LMCache, lmcache (PyPI). Vendors: LMCache, PyPI.

Quick answers

Is This vulnerability exploited in the wild?
No. Junglewise Threat Intelligence has no report of This vulnerability being exploited in the wild.
How severe is This vulnerability?
Critical severity, with a CVSS score of 9.8, published 7 October 2026.
Which products and versions are affected?
LMCache >= 0.3.9, < 0.5.6; lmcache (PyPI) >= 0.3.9, < 0.5.6, ECOSYSTEM:introduced=0.3.9.
Is there a fix for This vulnerability?
No fixed version is recorded yet. Check the vendor's advisory in the references below. If you run it, Junglewise drafts a mitigation that fits your setup and applies it once you approve, with senior security engineers behind it.
How is This vulnerability attacked?
It is attacked over the network, in a software library.
Am I affected?
Check whether you run LMCache or lmcache (PyPI) at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

Technical details

The vulnerability exists in the multiprocess (distributed) mode transport layer, which opens an unauthenticated ZeroMQ ROUTER socket and uses msgpack for message handling. Extension code 1 in msgpack messages is deserialized via pickle.loads in DeviceIPCWrapper.Deserialize before request validation, enabling remote code execution. Attack requires network access to the transport port (default 5555), with no authentication or user interaction required.

Affected products

  • LMCache LMCache >= 0.3.9, < 0.5.6

Timeline

  • 2026-10-07: disclosed
  • 2026-10-16: advisory: Advisory withdrawn as duplicate of GHSA-w5f2-9q9c-ff4h

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