{"schema":"threatline.record/2","record":{"id":"CVE-2026-77937","aliases":[],"summary":"Letta through 0.16.8 Cross-Tenant Impersonation via user_id Header","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.","categories":["Unclassified"],"product":"letta","vendor":"letta-ai","ecosystem":null,"affected_ranges":[{"source":"CVE List","source_url":"https://www.cve.org/CVERecord?id=CVE-2026-77937","source_modified_at":"2026-10-20T13:48:37.840Z","fetched_at":"2026-10-23T18:45:31.882637Z","product":"letta","vendor":"letta-ai","versions":[{"version":"0","lessThanOrEqual":"0.16.8","status":"affected","versionType":"semver"}],"defaultStatus":"unaffected"}],"fixed_versions":[],"cvss":8.6,"severity":"High","kev":{"listed":false},"epss":{"probability":0.00401,"percentile":0.33247,"score_date":"2026-10-23"},"published_at":"2026-10-20T00:46:14.829Z","modified_at":"2026-10-20T13:48:37.840Z","provenance":[{"source":"CVE List","url":"https://www.cve.org/CVERecord?id=CVE-2026-77937","fetched_at":"2026-10-23T18:45:31.882637Z","source_modified_at":"2026-10-20T13:48:37.840Z"},{"source":"EPSS","url":"https://api.first.org/data/v1/epss?cve=CVE-2026-77937","fetched_at":"2026-10-23T18:42:43.628194Z","source_modified_at":"2026-10-23"}],"sources":["CVE List","EPSS"],"references":[{"source":"CVE List","url":"https://www.lasso.security/vulnerability-database/cve-2026-77937","tags":["technical-description","exploit"]},{"source":"CVE List","url":"https://github.com/letta-ai/letta/blob/1131535716e8a31c9a437f8695e25ac98f203a24/letta/server/rest_api/dependencies.py#L39","tags":["technical-description"]},{"source":"CVE List","url":"https://www.vulncheck.com/advisories/letta-through-0.16.8-cross-tenant-impersonation-via-user-id-header","tags":["third-party-advisory"]}],"locations":[],"motoko_assessment":{"status":"requires_architecture_review","automatic_remediation":false},"cve_state":"PUBLISHED","cvss_source":"CVE List","ssvc":{"exploitation":"poc","automatable":"no","technical_impact":"total","assessed_at":"2026-10-20T13:48:24.242241Z"},"classification":{"method":"product-first software-layer rules","rules_version":"2.1","matched_on":null,"confidence":"unknown","reviewed":false},"change_timestamp":"2026-10-20T13:48:37.840Z","content_hash":"29b22d9ff2116e696fb0a1750be6c4d1a13a60576af9189ebbf3271f0528672e"}}