CVE-2026-77937 Letta - Authentication Bypass

Letta through 0.16.8 contains an authentication bypass caused by self-asserted user_id HTTP header, letting API callers impersonate other users to read and modify their agents, memory, and configuration, exploit requires crafted user_id header.

CVSS base score 8.1 /10
High
CISA KEV
Not listed
Public exploit
None known
Authentication
Required
View the NVD record ↗

Details

Type
Authentication Bypass
Impact
Broken Authentication, Data Tampering, Information Disclosure
CVSS vector
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:N
Published
20 October 2026
Updated
20 October 2026
Weakness
CWE-639

Vendor fix

Update to the latest version beyond 0.16.8.

Patching closes this CVE. It does not tell you which of your systems run the affected version, or what else is exposed alongside them.

References

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