Auth bypass in Letta-Ai Letta
CVE-2026-77937
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.
Vulnerability class: IDOR (Insecure Direct Object Reference)
Published · last modified .
CVSS v3 metric
CVSS v3 base score 8.1 (High). Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:N.
EPSS exploit prediction
No EPSS score from FIRST.org yet. New CVEs usually get one within a few days; no score means no signal yet, not low risk. How EPSS works.
Affected products
Weakness classification (CWE)
References
- github.com/letta-ai/letta/blob/1131535716e8a31c9a437f8695e25ac98f203a24/letta/s… (technical-description)
- www.lasso.security/vulnerability-database/cve-2026-77937 (technical-description, exploit)
- www.vulncheck.com/advisories/letta-through-0.16.8-cross-tenant-impersonation-vi… (third-party-advisory)
Frequently asked questions
- What is CVE-2026-77937?
- CVE-2026-77937 is a high-severity vulnerability in Letta-Ai Letta, classified under Authorization Bypass Through User-Controlled Key. CVSS score: 8.1/10. Published 2026-10-20.
- How severe is CVE-2026-77937?
- High severity. CVSS v3 base score is 8.1 out of 10.