CVE-2026-85664

Chroma 1.5.9, an open-source vector database, does not enforce upper bounds on the HNSW index parameters max_neighbors, ef_construction, and ef_search supplied in collection-create requests (CWE-770, allocation of resources without limits). An unauthenticated attacker with network access to the server's API can create a collection with arbitrarily large parameter values, causing the server to consume excessive memory during index compaction and crash or become unresponsive. The impact is high-severity denial of service only; per the CVSS 4.0 vector there is no loss of confidentiality or integrity. Any operator running the Chroma 1.5.9 server, especially instances reachable by untrusted or unauthenticated clients, is affected. Exploitation has not been observed: there is no known public proof-of-concept, it is not in CISA KEV, and EPSS estimates only a 0.4% chance of exploitation within 30 days.

What to do: Operators running Chroma 1.5.9 should restrict unauthenticated access to the server API (bind to localhost, apply firewall/ACL rules, or place the service behind an authenticated reverse proxy) and monitor Chroma process memory for abnormal growth. Until a patched release is published, cap max_neighbors, ef_construction, and ef_search to sane values in client code or at a validating proxy, and watch the chromadb project for an official fix and upgrade as soon as it is available.