CVE-2026-77937 HIGH

CVE-2026-77937: Letta through 0.16.8 Cross-Tenant Impersonation via user_id Header

Vendor Letta-Ai

Product letta

Weakness CWE-639 · IDOR

Published October 20, 2026

Last update October 20, 2026

View on NVD All CVEs

CVSS base score

8.6/10

Attack vector Network

Attack complexity Low

Privileges required Low

User interaction None

Confidentiality —

Integrity —

CVSS vector

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

What the vulnerability does

01Description

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.

Key dates

02Disclosure timeline

October 20, 2026 CVE published

October 20, 2026 Record updated

External resources

03References

NVD — National Vulnerability Database https://nvd.nist.gov/vuln/detail/CVE-2026-77937 CWE — Common Weakness Enumeration https://cwe.mitre.org/data/definitions/639.html AskarLabs — CWE-639 write-up Authorization Bypass Through User-Controlled Key

Related vulnerabilities

04Related CVE

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