Executive brief
Chroma is a vector database search infrastructure used to power AI applications. An unauthenticated attacker can send collection creation requests with extremely large values for HNSW index tuning parameters, causing the server to consume excessive memory and crash. This results in service unavailability and potential data loss during index operations.
Technical details
The vulnerability is an input validation flaw in Chroma 1.5.9's collection-create API endpoint. The HNSW (Hierarchical Navigable Small World) index parameters max_neighbors, ef_construction, and ef_search lack upper-bound validation, allowing unauthenticated attackers to supply arbitrarily large integer values. When the server attempts index compaction with these oversized parameters, it allocates excessive heap memory, triggering denial of service. The attack requires no authentication and is reachable over the network via the collection-create API. A patch implementing proper parameter bounds validation is required to remediate the issue.
Affected products
- Chroma Chroma 1.5.9
Timeline
- 2026-09-04: disclosed