Auth bypass in B3log Siyuan
CVE-2026-40259
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.
EPSS: 0.004 (32.7th percentile) — read the EPSS interpretation.
CVSS v3 metric
CVSS v3 base score 8.1 (High). Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:H/A:H.
Affected products
- B3log Siyuan
- Siyuan-note Siyuan — versions < 0.0.0-20260407035653-2f416e5253f1, < 3.6.4
Weakness classification (CWE)
References
- security-advisories@github.com (x_refsource_CONFIRM, Exploit, Third Party Advisory)
- security-advisories@github.com (x_refsource_MISC, Release Notes)
Frequently asked questions
- What is CVE-2026-40259?
- CVE-2026-40259 is a high-severity vulnerability in B3log Siyuan, classified under Improper Authorization. CVSS score: 8.1/10. Published 2026-04-16.
- How severe is CVE-2026-40259?
- High severity. CVSS v3 base score is 8.1 out of 10.