CVE-2026-77937: Authorization Bypass Through User-Controlled Key in letta-ai letta
Description
Letta versions up to 0.16.8 have an authentication bypass vulnerability that allows attackers to impersonate other users by setting a user_id HTTP header. This enables unauthorized reading and modification of another tenant's agents, memory, and configuration, even when LETTA_SERVER_SECURE is enabled. The vulnerability has a high severity with a CVSS score of 8.6.
CVSS v4.0
Score 8.6high
Affected software
letta-ai
letta
Run on your own infrastructure? Check whether these packages are installed with threat-finder — our free open-source scanner.
AI-Powered Analysis
Machine-generated threat intelligence
Technical Analysis
CVE-2026-77937 is an authentication bypass vulnerability in letta through version 0.16.8. The flaw allows API callers to impersonate other users by supplying a self-asserted user_id HTTP header. Attackers can specify the user_id of another tenant, bypassing authentication controls including the LETTA_SERVER_SECURE setting, thereby gaining unauthorized access to read and modify that user's agents, memory, and configuration data.
Potential Impact
An attacker can impersonate any user by manipulating the user_id HTTP header, leading to unauthorized access and modification of sensitive user data such as agents, memory, and configuration. This compromises tenant isolation and data confidentiality within the affected letta deployments.
Mitigation Recommendations
Patch status is not yet confirmed — check the vendor advisory for current remediation guidance. Until a fix is available, restrict API access to trusted users and monitor for suspicious use of the user_id header. Avoid exposing the API to untrusted networks.
Technical Details
- Data Version
- 5.2
- Assigner Short Name
- VulnCheck
- Date Reserved
- 2026-08-21T17:52:36.080Z
- Cvss Version
- 4.0
- State
- PUBLISHED
Threat ID: 6ad6c1992cdf04f656e4957a
Added to database: 10/20/2026, 01:19:21 UTC
Last enriched: 10/20/2026, 01:33:16 UTC
Last updated: 10/20/2026, 01:34:17 UTC
Views: 3
Community Reviews
0 reviewsCrowdsource mitigation strategies, share intel context, and vote on the most helpful responses. Sign in to add your voice and help keep defenders ahead.
Want to contribute mitigation steps or threat intel context? Sign in or create an account to join the community discussion.
Actions
Updates to AI analysis require Pro Console access. Upgrade inside Console → Billing.
Need more coverage?
Upgrade to Pro Console for AI refresh and higher limits.
For incident response and remediation, OffSeq services can help resolve threats faster.
Latest Threats
Check if your credentials are on the dark web
Instant breach scanning across billions of leaked records. Free tier available.