CVE-2026-77937

Letta through 0.16.8 Cross-Tenant Impersonation via user_id Header

Published Oct 20, 2026 CVSS 4.0 · 8.6 High EPSS < 1% KEV · Not listed
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.

Remediation

No solution or workaround provided in the CVE record

Tracking

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Advisories

No advisories available
History
Type Values Removed Values Added
First Time appeared Letta-ai
Letta-ai letta
Vendors & Products Letta-ai
Letta-ai letta
Type Values Removed Values Added
Metrics ssvc

{'options': {'Automatable': 'no', 'Exploitation': 'poc', 'Technical Impact': 'total'}, 'version': '2.0.3'}

Type Values Removed Values Added
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.
Title Letta through 0.16.8 Cross-Tenant Impersonation via user_id Header
First Time appeared Letta
Letta letta
Weaknesses CWE-639
CPEs cpe:2.3:a:letta:letta:*:*:*:*:*:*:*:*
Vendors & Products Letta
Letta letta
References
Metrics cvssV3_1

{'score': 8.1, 'vector': 'CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:N'}

cvssV4_0

{'score': 8.6, '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'}

Weaknesses

Sources

Status
PUBLISHED
Assigner
VulnCheck
Published
Updated
Oct 20, 2026, 1:48 PM
Reserved
Aug 21, 2026, 5:52 PM
Status
Deferred
Published
Oct 20, 2026, 1:17 AM
Modified
Oct 20, 2026, 8:11 PM