{"id":"CVE-2026-77937","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.","modified":"2026-10-20T10:47:24.494624228Z","published":"2026-10-20T00:46:14.829Z","database_specific":{"cna_assigner":"VulnCheck","cwe_ids":["CWE-639"],"osv_generated_from":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/77xxx/CVE-2026-77937.json"},"references":[{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/77xxx/CVE-2026-77937.json"},{"type":"PACKAGE","url":"https://github.com/letta-ai/letta"},{"type":"ARTICLE","url":"https://github.com/letta-ai/letta/blob/1131535716e8a31c9a437f8695e25ac98f203a24/letta/server/rest_api/dependencies.py#L39"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-77937"},{"type":"WEB","url":"https://pypi.org"},{"type":"EVIDENCE","url":"https://www.lasso.security/vulnerability-database/cve-2026-77937"},{"type":"ADVISORY","url":"https://www.vulncheck.com/advisories/letta-through-0.16.8-cross-tenant-impersonation-via-user-id-header"}],"affected":[{"ranges":[{"type":"GIT","repo":"https://github.com/letta-ai/letta","events":[{"introduced":"0"},{"last_affected":"1131535716e8a31c9a437f8695e25ac98f203a24"}],"database_specific":{"extracted_events":[{"strategy":"StandardRange","range":[{"introduced":"0"},{"last_affected":"0.16.8"}],"source":"AFFECTED_FIELD"}]}}],"versions":["0.16.8","0.16.7","0.16.6","0.16.5","0.16.4","0.16.2","0.16.1","0.16.0","0.15.1","0.15.0","0.14.0","0.13.0","0.12.1","0.12.0","0.11.7","0.11.6","0.11.5","0.11.4","0.11.3","0.11.2","0.11.1","0.11.0","0.10.1","0.10.0","0.9.0","0.9.1","0.8.17","0.8.16","0.8.15","0.8.14","0.8.13","0.8.12","0.8.11","0.8.10","0.8.9","0.8.8","0.8.7","0.8.6","0.8.5","0.8.4","0.8.3","0.8.2","0.8.1","0.8.0","0.7.29","0.7.28","0.7.27","0.7.26","0.7.25","0.7.24","0.7.23","0.7.22","0.7.21","0.7.20","0.7.19","0.7.18","0.7.17","0.7.16","0.7.15","0.7.14","0.7.13","0.7.12","0.7.11","0.7.10","0.7.9","0.7.8","0.7.7","0.7.6","0.7.5","0.7.4","0.7.3","0.7.2","0.7.1","0.6.54","0.7.0","0.6.53","0.6.52","0.6.51","0.6.50","0.6.49","0.6.48","0.6.47","0.6.46","0.6.45","0.6.44","0.6.43","0.6.42","0.6.41","0.6.40","0.6.39","0.6.37","0.6.36","0.6.35","0.6.34","0.6.33","0.6.32","0.6.31","0.6.30","0.6.29","0.6.28","0.6.27","0.6.26","0.6.25","0.6.24","0.6.23","0.6.22","0.6.21","0.6.20","0.6.19","0.6.18","0.6.17","0.6.16","0.6.15","0.6.14","0.6.13","0.6.12","0.6.11","0.6.10","0.6.9","0.6.8","0.6.7","0.6.6","0.6.5","0.6.4","0.6.3","0.6.2","0.6.1","0.6.0","0.5.4","0.5.3","0.5.2","0.5.1","0.5.0","0.4.1","0.4.0","0.3.24","0.3.23","0.3.22","0.3.21","0.3.20","0.3.19","0.3.18","0.3.17","0.3.16","0.3.15","0.3.14","0.3.13","0.3.12","0.3.11","0.3.10","0.3.9","0.3.8","0.3.7","0.3.6","0.3.5","0.3.4","0.3.3","0.3.2","0.3.1","0.3","0.2.11","0.2.10","0.2.9","0.2.8","0.2.7","0.2.6","0.2.5","0.2.4","0.2.3","0.2.2","0.2.1","0.2.0","0.1.15","0.1.14","0.1.13","0.1.12","0.1.6"],"database_specific":{"source":"https://storage.googleapis.com/osv-test-cve-osv-conversion/osv-output/CVE-2026-77937.json"}}],"schema_version":"1.9.1","severity":[{"type":"CVSS_V4","score":"CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N"}]}