{"id":"CVE-2026-77937","aliases":[],"url":"https://o3.security/vulnerability/CVE-2026-77937","summary":"Letta through 0.16.8 contains an authentication bypass vulnerability that allows API callers to impersonate other users by supplying a self-asserted user_id HTTP header. Attackers can…","details":"Letta through 0.16.8 contains an authentication bypass vulnerability that allows API callers to impersonate other users by supplying a self-asserted user_id HTTP header. Attackers can set user_id to another tenant's ID, even with LETTA_SERVER_SECURE enabled, to read and modify that user's agents, memory and configuration.","published":"2026-10-20T01:17:20.263","modified":"2026-10-20T01:17:20.263","cvss":{"score":8.1,"severity":"HIGH","vector":"CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:N"},"epss":null,"cisaKev":null,"exploitsKnown":null,"affectedPackages":[],"fix":null,"references":[{"type":"WEB","url":"https://github.com/letta-ai/letta/blob/1131535716e8a31c9a437f8695e25ac98f203a24/letta/server/rest_api/dependencies.py#L39"},{"type":"WEB","url":"https://www.lasso.security/vulnerability-database/cve-2026-77937"},{"type":"WEB","url":"https://www.vulncheck.com/advisories/letta-through-0.16.8-cross-tenant-impersonation-via-user-id-header"}],"provenance":{"sources":["OSV.dev","NVD","FIRST.org (EPSS)"],"lastVerified":"2026-10-20T01:17:20.263"}}