LibreChat EUVD-2026-39458

Exploitation requires a valid authenticated user session on the target LibreChat instance (PR:L per CVSS vector) - unauthenticated exploitation is not possible. The instance must be running any version prior to 0.8.4-rc1, and the POST /api/convos/duplicate endpoint must be network-reachable (AV:N). No special configuration or feature flag is required beyond default LibreChat deployment with user accounts enabled. Exploitation is bounded by the following limiting factors: (1) the attacker must hold a valid account, restricting external threat to instances with open or easily obtained registration; (2) private single-user deployments face no external threat but retain insider risk; (3) the severity of resource exhaustion scales with server hardware capacity - well-provisioned deployments may require a higher request volume before service degradation becomes observable.

The CVSS 3.1 score of 6.5 (AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H) accurately reflects the risk profile: the attack is network-accessible, requires low complexity, demands only a low-privileged (authenticated) account, and yields full availability impact with no confidentiality or integrity consequence. No EPSS data was provided in the input - exploitation probability cannot be quantified. The vulnerability is not listed in CISA KEV and no public exploit code has been identified. However, the bypass nature materially elevates practical risk: deployments that patched CVE-2025-7105 and consider themselves protected are still exposed. The attack requires no special tooling - any HTTP client in a loop suffices - making exploitation accessible to any authenticated user. The primary concern is service disruption against shared or public-facing LibreChat instances; single-user or air-gapped deployments face minimal external threat but remain vulnerable to insider abuse.

An authenticated user on a public or shared LibreChat instance - including a self-registered account - sends a high-frequency loop of POST requests to /api/convos/duplicate using standard HTTP tooling such as curl or a simple script. Each request triggers expensive database duplication operations with no server-side throttling, rapidly consuming database connection pool capacity, CPU, or memory. This degrades or denies service for all concurrent users on the instance without requiring any elevated privileges or special configuration.