siyuan-note SiYuan up to 3.7.3 Authentication Middleware CheckAuth token improper authorization

Summaryinfo

A vulnerability classified as critical was found in siyuan-note SiYuan up to 3.7.3. Affected by this vulnerability is the function CheckAuth of the component Authentication Middleware. Such manipulation of the argument token leads to improper authorization. This vulnerability is referenced as CVE-2026-73056. It is possible to launch the attack remotely. No exploit is available.

Detailsinfo

A vulnerability, which was classified as critical, has been found in siyuan-note SiYuan up to 3.7.3. Affected by this issue is the function CheckAuth of the component Authentication Middleware. The manipulation of the argument token with an unknown input leads to a improper authorization vulnerability. Using CWE to declare the problem leads to CWE-285. The product does not perform or incorrectly performs an authorization check when an actor attempts to access a resource or perform an action. Impacted is confidentiality, integrity, and availability. CVE summarizes:

SiYuan kernel versions before 3.7.4 contain an improper restriction of excessive authentication attempts vulnerability in the CheckAuth() middleware. The middleware accepts the API token (Conf.Api.Token) via an Authorization header (Token/Bearer) or a ?token= query parameter, and neither path is protected by the application's CAPTCHA/lockout mechanism (NeedCaptcha/WrongAuthCount). As a result, an unauthenticated remote attacker can perform unlimited automated guesses of the API token, particularly when a short or weak custom token has been configured, and upon success gains full RoleAdministrator access enabling arbitrary file operations and SQL queries.

The advisory is shared for download at github.com. This vulnerability is handled as CVE-2026-73056 since 08/10/2026. The exploitation is known to be easy. The attack may be launched remotely. No form of authentication is required for exploitation. There are known technical details, but no exploit is available. The MITRE ATT&CK project declares the attack technique as T1548.002.

Upgrading to version 3.7.4 eliminates this vulnerability.

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Productinfo

Vendor

• siyuan-note

Name

• SiYuan

Version

• 3.7.0
• 3.7.1
• 3.7.2
• 3.7.3

Website

• Product: https://github.com/siyuan-note/siyuan/

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