CVE-2026-77937 Details
Description
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.
A vulnerability in Letta versions through 0.16.8 allows API callers to bypass authentication and impersonate other users by sending a self-asserted user_id HTTP header. This flaw enables access to read and modify the targeted user's agents, memory, and configuration, even with the LETTA_SERVER_SECURE option enabled. The vulnerability arises because the application accepts the user_id header without verification against authenticated sessions, allowing any caller to manipulate data across different tenants.
It is recommended to replace the self-asserted user_id header with per-tenant credentials or tokens that verify the identity of the caller before granting access to tenant-specific data.
Metrics
CVSS 4.0 Severity and Vector Strings:
VolerionCVSS 3.x Severity and Vector Strings:
No data available for CVSS Version 2.0 on this CVE.
Volerion
Assessed Oct 20, 2026CISA-ADP
Assessed Oct 20, 2026References to Advisories, Solutions, and Tools
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Weakness Enumeration
| CWE-ID | CWE Name | Source |
|---|---|---|
| CWE-639 | Authorization Bypass Through User-Controlled Key | [email protected] |
Affected Products
| Product | Versions |
|---|---|
| Letta | <= 0.16.8 (semver) |
CPE
Remediation
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Change History
2 change records found show changes
| Date | Action | Recorded By |
|---|---|---|
| Oct 20, 2026 | CVE Modified | CISA-ADP |
| Oct 20, 2026 | New CVE Received | [email protected] |