CVE-2026-77937

What it is

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.

At a glance

Exploitability

Can be exploited over the network with a low-privilege account. High risk of data exposure, data tampering.

Exploit odds

0.5% chance of exploitation in the next 30 days (EPSS).

Fix

No patch or advisory is linked yet. Look at mitigations or restrict exposure.

Timeline

1. 2026-08-21 17:52 UTC ReservedThe CVE id was reserved by its CNA
2. 2026-10-20 01:17 UTC PublishedDisclosed publicly on CVE.org and NVD
3. 2026-10-20 20:11 UTC Last updatedMost recent change to the record

Details

Published

2026-10-20 01:17 UTC

Last modified

2026-10-20 20:11 UTC

Exploit probability

0.5% · EPSS, next 30 days

Weakness

CWE-639 · Insecure direct object reference

Record status

Deferred

Attack profile CVSS 4.0 · 8.6

Attack vector

Network

Complexity

Low

Attack requirements

None

Privileges needed

Low

User interaction

None

Confidentiality

High

Integrity

High

Availability

None