CVE-2026-77937
8.1HighPublished 20 Oct 2026 · NVD status: Received · AI triage by gemini-3.8-flash
- Attack vector
- Network
- Complexity
- Low
- Privileges needed
- Low
- User interaction
- None
- Impact
- High impact on confidentiality, integrity
- Weakness
- CWE-639
Impact
Authenticated attackers can access, alter, or hijack other users' agents, memory, and configurations across tenants. They only need network access to the API and standard user credentials to supply a forged header.
Root cause
The REST API blindly trusts a user-supplied user_id HTTP header to establish identity instead of deriving it from the authenticated session.
Affected systems
Letta through 0.16.8
CVSS v3.1 · CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:N
Fix & remediation
Upgrade to a release newer than 0.16.8 once available. If patching must wait, configure a reverse proxy or API gateway in front of Letta to strip incoming user_id headers from client requests.
$ pip install --upgrade lettaAI-suggested. Run it in staging first and check it against the vendor advisory. Why?
NVD 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.