{
  "affected": [
    {
      "ranges": [
        {
          "database_specific": {
            "extracted_events": [
              {
                "range": [
                  {
                    "introduced": "0"
                  },
                  {
                    "last_affected": "0.16.8"
                  }
                ],
                "source": "AFFECTED_FIELD",
                "strategy": "StandardRange"
              }
            ]
          },
          "events": [
            {
              "introduced": "0"
            },
            {
              "last_affected": "1131535716e8a31c9a437f8695e25ac98f203a24"
            }
          ],
          "repo": "https://github.com/letta-ai/letta",
          "type": "GIT"
        }
      ]
    }
  ],
  "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"
  },
  "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.",
  "id": "CVE-2026-77937",
  "modified": "2026-10-21T02:30:45.957776008Z",
  "published": "2026-10-20T00:46:14.829Z",
  "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"
    }
  ],
  "schema_version": "1.9.0",
  "severity": [
    {
      "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",
      "type": "CVSS_V4"
    }
  ],
  "summary": "Letta through 0.16.8 Cross-Tenant Impersonation via user_id Header"
}