Milvus EUVD-2026-34292

Local authenticated access with low privileges (PR:L, AV:L per CVSS) on a host running milvus-io/milvus 2.6.13 or earlier is required. The vulnerability specifically affects the RBAC grantee ID mechanism within the etcd-backed KV metadata catalog - deployments that do not use Milvus RBAC features have a reduced attack surface. High attack complexity (AC:H) requires the attacker to possess specialized knowledge of the legacy 16-character hash format, the etcd key schema, and Milvus's grantee ID namespace. Limiting factors: no remote exploitation path exists (AV:L enforces local access only); the attacker must already hold a valid low-privilege account on the Milvus host; and the high complexity barrier significantly restricts exploitation to targeted, knowledge-intensive attacks rather than opportunistic mass exploitation. No special non-default configuration flag is documented as a prerequisite beyond RBAC being in use.

The CVSS 3.1 score of 4.5 reflects Medium severity driven by local-only attack vector (AV:L), high attack complexity (AC:H), low privilege requirement (PR:L), and uniformly low CIA impact (C:L/I:L/A:L). The temporal modifier E:P confirms proof-of-concept code exists, while RL:O indicates an official fix is available and RC:C confirms the report. No EPSS score was provided, but given the local-only vector and high complexity, opportunistic or widespread exploitation is unlikely - this is primarily a threat from malicious insiders or attackers who have already achieved a foothold. The absence from CISA KEV is consistent with the constrained attack surface. Real-world priority is moderate for multi-tenant Milvus deployments where RBAC is actively used; organizations relying solely on Milvus's grantee system to enforce privilege separation face the highest residual risk. The high attack complexity rating is the key limiting signal - this is not a trivially exploitable flaw.

A low-privileged local attacker with knowledge of Milvus's legacy 16-character grantee ID hashing scheme - informed by the publicly disclosed proof-of-concept at GitHub issue #49857 - enumerates existing grantee IDs from etcd, identifies collision candidates or predicts IDs for high-privilege roles, then manipulates the KV metadata store to associate their own account with an elevated grantee ID. The high attack complexity means the attacker must understand both the truncated hash algorithm and the etcd key structure, limiting this to technically proficient adversaries. Success yields low-level unauthorized read and write access to Milvus metadata and resource access controls.