CVE-2026-44649
Published: 29 May 2026
Summary
CVE-2026-44649 is a critical-severity Authentication Bypass by Spoofing (CWE-290) vulnerability. Its CVSS base score is 9.8 (Critical).
Operationally, exploitation aligns with the MITRE ATT&CK technique Exploit Public-Facing Application (T1190); ranked at the 12.2th percentile by exploit likelihood (below the median); it is not currently listed in the CISA KEV catalog.
OWASP Top 10 for Web (2025)
EU & UK References
- 🇪🇺 ENISA EUVD: EUVD-2026-33401
Vulnerability details
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…
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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.
- CWE(s)
Related Threats
MITRE ATT&CK Enterprise TechniquesAI
Why these techniques?
Auth bypass via unvalidated HTTP headers on a reachable web UI directly enables exploitation of a public-facing application (T1190).
Affected Assets
Mitigating Controls
Likely Mitigating Controls AI
Per-CVE control mapping for this CVE has not run yet; the list below is derived from the weakness types (CWEs) cited in the NVD entry.
Mandates authentication prior to establishing communications with services, preventing missing authentication for this critical function.
Requires authentication of devices prior to connection, preventing exploitation of missing authentication for critical network functions.
Requires authentication for non-organizational users, preventing access to critical functions without proper identification and authentication.
Isolated trusted path ensures the user interacts only with genuine system components, preventing spoofing of authentication interfaces or prompts.
Directly counters DNS response spoofing by requiring cryptographic origin authentication artifacts from the authoritative source.
Directly counters DNS response spoofing by requiring cryptographic origin authentication before trusting resolved names/addresses.
Requires cryptographic or protocol-level verification that blocks spoofed session establishment or continuation.
Ensures critical input functions cannot be reached without prior authorization.