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Description

SillyTavern is a locally installed user interface that allows users to interact with text generation large language models, image generation engines, and text-to-speech voice models. Prior to 1.18.0, SillyTavern accepts Remote-User (Authelia) and X-Authentik-Username (Authentik) HTTP headers to automatically log in users when SSO is configured. There is no validation that these headers originate from a trusted reverse proxy. Any network client that can reach the SillyTavern port directly can inject these headers and authenticate as any user, including administrators, without a password. This vulnerability is exploitable only when sso.autheliaAuth: true or sso.authentikAuth: true is set in config.yaml (both default to false). This vulnerability is fixed in 1.18.0.

PUBLISHED Reserved 2026-05-07 | Published 2026-05-29 | Updated 2026-06-02 | Assigner GitHub_M




CRITICAL: 9.8CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

Problem types

CWE-290: Authentication Bypass by Spoofing

CWE-306: Missing Authentication for Critical Function

CWE-346: Origin Validation Error

CWE-807: Reliance on Untrusted Inputs in a Security Decision

Product status

< 1.18.0
affected

References

github.com/...Tavern/security/advisories/GHSA-gxx6-h3g6-vwjh exploit

github.com/...Tavern/security/advisories/GHSA-gxx6-h3g6-vwjh

cve.org (CVE-2026-44649)

nvd.nist.gov (CVE-2026-44649)

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