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CVE-2026-40259

B3log Siyuan broken access control

8.1 HIGHPublic exploitEPSS 0.54%
  1. Published16 Apr 2026

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.

CVSS 3.1 breakdown

Attack vectorNetwork
Attack complexityLow
Privileges requiredLow
User interactionNone
ScopeUnchanged
ConfidentialityNone
IntegrityHigh
AvailabilityHigh
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:H/A:H

Affected products

B3log Siyuan< 3.6.4

Remediation

Fixed in
B3log Siyuan≥ 3.6.4

References

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Frequently asked

Is CVE-2026-40259 being actively exploited?

CVE-2026-40259 is not in the CISA KEV catalog. A public exploit reference exists, so treat it as exploitable. Its EPSS exploit probability is 0.54%.

How severe is CVE-2026-40259?

CVE-2026-40259 has a CVSS 3.1 base score of 8.1, rated high. EPSS estimates a 0.54% probability of exploitation.

Which products are affected by CVE-2026-40259?

Affected products include B3log Siyuan.

How do I fix CVE-2026-40259?

Upgrade affected software to a fixed version, for example B3log Siyuan 3.6.4 or later, then confirm no affected versions remain in your inventory.

How Secuno handles this

Secuno correlates vulnerabilities like CVE-2026-40259 against the real software inventory on every managed device, every day. Rather than a static severity, each match is scored in context: exploit availability, EPSS, the asset's exposure, and business criticality decide where it lands in the queue. If an affected version is present anywhere across your portfolio, it surfaces automatically with a prioritised remediation path.

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Data from the NVD, CISA KEV catalog and FIRST EPSS. CVSS 3.1 base score shown where available.