CVE-2026-77937CWE-639

CVE-2026-77937

High · published October 20, 2026

CVSS v3.1
8.1
EPSS
0%
Percentile
33.2
In the wild
Unconfirmed
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.

The record
Technical detail
CVSS v3.1
8.1 · HIGH
Vector
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:N
CVSS v4.0
8.6 · 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
EPSS
0.00401 · 33.2th percentile
Weakness
CWE-639 · Authorization Bypass Through User-Controlled Key
Published
2026-10-20T05:17Z
References (3)
https://github.com/letta-ai/letta/blob/1131535716e8a31c9a437f8695e25ac98f203a24/letta/server/rest_api/dependencies.py#L39 · [email protected]https://www.lasso.security/vulnerability-database/cve-2026-77937 · [email protected]https://www.vulncheck.com/advisories/letta-through-0.16.8-cross-tenant-impersonation-via-user-id-header · [email protected]
EPSS history
Timeline
  • 21 OCT 03:32Z
    EPSS moved — → 0%
    epss
  • 20 OCT 00:46Z
    Letta through 0.16.8 Cross-Tenant Impersonation via user_id Header
    cvelistv5
  • 20 OCT 00:46Z
    Letta through 0.16.8 Cross-Tenant Impersonation via user_id Header
    cvelistv5