Lmcache

LMCache multiprocess mode, also called distributed mode, opens an unauthenticated ZeroMQ ROUTER so worker processes can register and share KV cache blocks. Messages on that socket are msgpack. Extension code 1 is passed to DeviceIPCWrapper.Deserialize, which calls pickle.loads, while the server is still decoding request arguments and before the handler runs. A single unauthenticated ZMQ DEALER message to the transport port (default 5555) therefore executes code as the user the LMCache process runs as. Official container images run that process as root. The transport binds to localhost unless the operator sets a routable address with --host, which is how multi-node deployments let peers connect. The decode path shipped in v0.3.9 and is present through v0.5.5, including the v0.5.6 release candidates. v0.5.6, published on 2026-10-14, removes pickle.loads from this path.

Published: 2026-10-07T09:40:11.449Z
Updated: 2026-10-29T10:24:45.984Z

A flaw has been found in LMCache up to 0.5.4. This affects the function hex_hash_to_int16 of the file lmcache/integration/vllm/utils.py of the component KV Cache Handler. Executing a manipulation can lead to use of weak hash. The attack needs to be launched locally. The attack requires a high level of complexity. It is indicated that the exploitability is difficult. The exploit has been published and may be used. Upgrading to version 0.5.5 is able to mitigate this issue. This patch is called ce08eea76ce5898200efee55f4932fd07a7cabeb. It is suggested to upgrade the affected component. A contributor of the project confirms: "hex_hash_to_int16() was introduced in 0.3.1 (PR #882, commit f5174701). It is not present in 0.3.0, and it is still present in 0.4.7 through 0.5.4."

Published: 2026-06-04T14:45:10.552Z
Updated: 2026-10-17T06:18:40.529Z