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CVE-2026-44649 SillyTavern CVE debrief

SillyTavern versions prior to 1.18.0 fail to validate that Remote-User (Authelia) and X-Authentik-Username (Authentik) HTTP headers originate from a trusted reverse proxy. When SSO is enabled via sso.autheliaAuth: true or sso.authentikAuth: true in config.yaml, any network client with direct access to the SillyTavern port can inject these headers to authenticate as arbitrary users, including administrators, without credentials. Both SSO options default to false, limiting exposure to explicitly configured instances. The vulnerability was disclosed on 2026-05-29 and is resolved in version 1.18.0.

Vendor
SillyTavern
Product
Unknown
CVSS
CRITICAL 9.8
CISA KEV
Not listed in stored evidence
Original CVE published
2026-05-29
Original CVE updated
2026-07-22
Advisory published
2026-05-29
Advisory updated
2026-07-22

Who should care

Organizations running SillyTavern with SSO authentication enabled (sso.autheliaAuth: true or sso.authentikAuth: true) are at critical risk. System administrators, security teams, and users hosting SillyTavern instances accessible from untrusted networks should prioritize patching. The default configuration (both SSO options disabled) is not vulnerable.

Technical summary

The vulnerability exists in SillyTavern's SSO authentication implementation. When sso.autheliaAuth or sso.authentikAuth is enabled in config.yaml, the application accepts Remote-User or X-Authentik-Username HTTP headers to automatically authenticate users. The application does not verify that these headers are set by a trusted reverse proxy, allowing any client with network access to the application port to supply arbitrary header values and impersonate any user account. This represents a complete authentication bypass when SSO is enabled. The fix in version 1.18.0 adds validation to ensure headers originate from trusted sources.

Defensive priority

critical

Recommended defensive actions

  • Upgrade SillyTavern to version 1.18.0 or later
  • If immediate patching is not possible, disable sso.autheliaAuth and sso.authentikAuth in config.yaml (set both to false)
  • Configure network-level access controls to restrict direct access to SillyTavern ports, ensuring all traffic passes through a trusted reverse proxy that strips or validates authentication headers
  • Review authentication logs for anomalous header-based login attempts prior to the fix date
  • Verify reverse proxy configuration properly strips or overwrites Remote-User and X-Authentik-Username headers from untrusted sources

Evidence notes

Vulnerability confirmed by GitHub Security Advisory GHSA-gxx6-h3g6-vwjh. CVSS 3.1 score 9.8 (Critical) assigned. CWE-290 (Authentication Bypass by Spoofing), CWE-306 (Missing Authentication for Critical Function), CWE-346 (Origin Validation Error), and CWE-807 (Reliance on Untrusted Inputs in a Security Decision) identified. Fix version 1.18.0 confirmed.

Sources and references

Verified primary and authoritative sources

  • CVE-2026-44649 CVE Program record

    Publisher, destination, and source semantics verified

    URL: https://www.cve.org/CVERecord?id=CVE-2026-44649

    CVE Program - Official CVE Program record with source-provided CVE metadata.

  • CVE-2026-44649 NVD vulnerability detail

    Publisher, destination, and source semantics verified

    URL: https://nvd.nist.gov/vuln/detail/CVE-2026-44649

    NIST National Vulnerability Database - Official NIST NVD detail page and source-specific vulnerability assessment.

Supplemental references

Methodology and review provenance

AI-assisted synthesis based on stored public vulnerability evidence. System validation, approval state, and publication status do not by themselves establish human review of this revision. PatchSiren helps prioritize defensive review and does not prove exposure or remediation on any system.