CVE-2026-40259
HIGHSiYuan 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…
EPSS Exploitation Probability
EPSS (Exploit Prediction Scoring System) is a daily probability model maintained by FIRST.org. It estimates the likelihood a CVE will be exploited in production environments within the next 30 days, derived from real-world threat intelligence signals.
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.
Affected Products
siyuanb3logDetection & mitigation playbook
Vendor / applianceDetect
Inventory every b3log siyuan deployment and check each version against the affected-products list above. Because the exploit targets the running system rather than your application code, also watch for exploitation at the network and runtime layer — O3 flags the exploit behaviour from runtime telemetry and egress traffic even before a vulnerable build is confirmed.
Fix
Apply the b3log siyuan security patch or hotfix for CVE-2026-40259 on the affected version, following the vendor advisory for your exact build.
Workarounds
Cut exposure now: restrict the management/admin interface to trusted networks, segment the device, and apply the vendor's recommended configuration mitigations and any WAF/IPS signature. O3's runtime protection blocks the exploit chain at execution, holding the line on unpatched or end-of-life systems until you can patch.
How O3 protects you
O3 detects and blocks CVE-2026-40259 exploitation at runtime: eBPF exploit-chain detection, plus L7 egress monitoring that catches the post-exploitation callback and severs the attacker's outbound channel.
Tailored to CVE-2026-40259. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
Frequently Asked Questions
Is CVE-2026-40259 being exploited in your environment?
O3's eBPF runtime sensors and L7 egress monitoring detect and block the CVE-2026-40259 exploit chain at execution — protecting unpatched and end-of-life systems until the vendor patch is applied.