Is CVE-2026-40259 in the CISA KEV catalog?

No. CVE-2026-40259 is not currently on the CISA Known Exploited Vulnerabilities list.

What is the CVSS severity of CVE-2026-40259?

CVE-2026-40259 has a CVSS v3 base score of 8.1 (HIGH).

What is the EPSS score for CVE-2026-40259?

CVE-2026-40259 has an EPSS score of 0.40% (32th percentile), estimating the probability of exploitation in the next 30 days.

CVE & CISA-KEV Catalog

CVE-2026-40259

HIGH

8.1

CVSS v3

NVD

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-285

CVSS v3 Vector

Exploitability

Attack VectorNetwork

Attack ComplexityLow

Privileges RequiredLow

User InteractionNone

ScopeUnchanged

Impact

ConfidentialityNone

IntegrityHigh

AvailabilityHigh

CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:H/A:H

Exploit Intelligence

0.40%probability of exploitation in 30 days

32ndpercentile

Low risk: more likely to be exploited than 32% of all known CVEs.

References

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This product uses NVD data but is not endorsed or certified by the NVD. EPSS scores courtesy of FIRST.org (https://www.first.org/epss). Source: CISA KEV Catalog. Data as of 2026-04-20.