CVE-2026-40259: b3log siyuan Improper Authorization

Vulnerability summary

CVE-2026-40259 is a high (CVSS 8.1) Improper Authorization vulnerability in b3log siyuan. EPSS estimates a 0.54% chance of exploitation in the next 30 days, higher than 44.1% of scored vulnerabilities. 1 public exploit is recorded.

Timeline

1. 16-04-2026
   PublishedVulnerability first disclosed.
2. 20-04-2026
   Last modifiedVulnerability information updated.

Description

SiYuan is an open-source personal knowledge management system. In versions 3.6.3 and below, the /api/av/removeUnusedAttributeView endpoint is protected only by generic authentication that accepts publish-service RoleReader tokens. The handler passes a caller-controlled id directly to a model function that unconditionally deletes the corresponding attribute view file from the workspace without verifying that the caller has write privileges or that the target attribute view is actually unused. An authenticated publish-service reader can permanently delete arbitrary attribute view definitions by extracting publicly exposed data-av-id values from published content, causing breakage of database views and workspace rendering until manually restored. This issue has been fixed in version 3.6.4.

• CWE-285Improper AuthorizationThe product does not perform or incorrectly performs an authorization check when an actor attempts to access a resource or perform an action.