Cyber Resilience

CVE-2026-40318

B3Log Siyuan ≤ 3.6.4

Published
16 April 2026
Modified
20 April 2026
CVSS Score v3.1 8.5
Click a component to see what it means
Raw vectorCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:N/I:L/A:H
EPSS Score 0.0029 21th percentile
Risk Priority 58 floored blend · peak EPSS

Summary

CVE-2026-40318 is a high-severity Path Traversal: '../filedir' (CWE-24) vulnerability in B3Log Siyuan. Its CVSS base score is 8.5 (High).

Operationally, exploitation aligns with the MITRE ATT&CK technique Data from Local System (T1005); ranked at the 21th percentile by exploit likelihood (below the median); it is not currently listed in the CISA KEV catalog.

The strongest mitigations our analysis identified map to SI-10 (Information Input Validation) and AC-3 (Access Enforcement) — see the control section below for these in your framework.

Deeper analysis AI-assisted summary

Synthesised by an AI model from the NVD description and linked references — a reading aid, not an authoritative source.

CVE-2026-40318 is a path traversal vulnerability (CWE-24) in SiYuan, an open-source personal knowledge management system. The issue affects versions 3.6.3 and prior, where the /api/av/removeUnusedAttributeView endpoint constructs filesystem paths using a user-controlled id parameter without validation or path boundary checks. This allows attackers to inject traversal sequences like ../ to access and delete files outside the intended directory, targeting arbitrary .json files such as global configuration files and workspace metadata. The vulnerability carries a CVSS v3.1 base score of 8.5 (AV:N/AC:L/PR:L/UI:N/S:C/C:N/I:L/A:H).

An authenticated attacker with low privileges (PR:L) can exploit this over the network with low complexity and no user interaction required. By crafting a malicious id parameter in requests to the endpoint, they can traverse directories and delete critical .json files, potentially disrupting system configuration, workspace data, and overall availability, while achieving low integrity impact through unauthorized deletions.

The vulnerability has been addressed in SiYuan version 3.6.4. Security practitioners should upgrade to this patched release, as detailed in the project's release notes (https://github.com/siyuan-note/siyuan/releases/tag/v3.6.4) and GitHub Security Advisory (https://github.com/siyuan-note/siyuan/security/advisories/GHSA-vw86-c94w-v3x4).

EU & UK References

Vulnerability Data

SiYuan is an open-source personal knowledge management system. In versions 3.6.3 and prior, the /api/av/removeUnusedAttributeView endpoint constructs a filesystem path using the user-controlled id parameter without validation or path boundary enforcement. An attacker can inject path traversal sequences such as…

more

../ into the id value to escape the intended directory and delete arbitrary .json files on the server, including global configuration files and workspace metadata. This issue has been fixed in version 3.6.4.

CWE(s)
CWE-24

Related Threats

MITRE ATT&CK Enterprise Techniques

T1005 Data from Local System Collection
Adversaries may search local system sources, such as file systems, configuration files, local databases, virtual machine files, or process memory, to find files of interest and sensitive data prior to Exfiltration.
attack.mitre.org →
T1190 Exploit Public-Facing Application Initial Access
Adversaries may attempt to exploit a weakness in an Internet-facing host or system to initially access a network.
attack.mitre.org →
Derived from this CVE’s CWE(s) via the direct CWE→ATT&CK cross-walk.

CVEs Like This One

CVE-2026-30869Same product: B3Log Siyuan
CVE-2026-33670Same product: B3Log Siyuan
CVE-2026-25539Same product: B3Log Siyuan
CVE-2026-32749Same product: B3Log Siyuan
CVE-2026-23851Same product: B3Log Siyuan
CVE-2024-55658Same product: B3Log Siyuan
CVE-2025-67488Same product: B3Log Siyuan
CVE-2024-53507Same product: B3Log Siyuan
CVE-2026-23850Same product: B3Log Siyuan
CVE-2026-32747Same product: B3Log Siyuan

Affected Assets

b3log
siyuan
≤ 3.6.4

Mitigating Controls

Mitigating Controls (NIST 800-53 r5) AI

SI-10 Information Input Validation good match

Input validation directly neutralizes '../' sequences in externally-supplied pathnames before they are resolved.

AC-3 Access Enforcement partial match

Enforced access authorizations can limit the damage even when path traversal succeeds.

Mitigating Controls (NIST CSF 2.0) AI

Derived directly from the weakness types (CWEs) cited in the NVD entry via our AI-authored CWE→CSF cross-walk (authority under review) — links open the control.

PR.PS-06 mostly match
prevents

Secure SDLC practices directly require input validation and path sanitization that prevent ../ traversal.

Mitigating Controls (ISO/IEC 27001:2022 Annex A) AI

Derived directly from the weakness types (CWEs) cited in the NVD entry via our AI-authored CWE→ISO cross-walk (authority under review) — links open the control.

A.8.28 Secure coding mostly match
prevents

Secure coding standards require neutralizing ../ sequences and canonicalizing paths before file operations.

A.8.29 Security testing in development and acceptance mostly match
finds

Security testing in development catches path-traversal flaws before release.

A.8.25 Secure development life cycle partial match
prevents

Secure SDLC mandates input validation and path canonicalization that directly block ../ traversal.

A.8.26 Application security requirements partial match
prevents

Application security requirements explicitly call for controls against path traversal in file-handling functions.

A.8.27 Secure system architecture and engineering principles partial match
prevents

Secure architecture principles reduce attack surface but do not prescribe the specific coding fix.

A.8.3 Information access restriction partial match
mitigates

Information access restriction limits which files can be reached, mitigating impact of traversal.

References