Cyber Resilience

CVE-2026-23850

Path Traversal in B3Log Siyuan ≤ 3.5.4

Public PoCPath Traversal
Published
19 January 2026
Modified
30 January 2026
Patch / advisory
View advisory
CVSS Score v4 8.8
Click a component to see what it means
Raw vectorCVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:L/VA:N/SC:N/SI:N/SA:N/E:P/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X
EPSS Score 0.0052 42th percentile
Risk Priority 45 floored blend · peak EPSS

Summary

CVE-2026-23850 is a high-severity Path Traversal (CWE-22) vulnerability in B3Log Siyuan. Its CVSS base score is 8.8 (High).

Operationally, exploitation aligns with the MITRE ATT&CK technique Exploit Public-Facing Application (T1190); ranked at the 42th percentile by exploit likelihood (below the median); it is not currently listed in the CISA KEV catalog; a public proof-of-concept is referenced.

The strongest mitigations our analysis identified map to AC-3 (Access Enforcement) and SI-10 (Information Input Validation) — 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-2026-23850 is a vulnerability in SiYuan, a personal knowledge management system, affecting versions prior to 3.5.4. The issue lies in the markdown feature, which performs unrestricted server-side HTML rendering, enabling arbitrary file read, referred to as Local File Disclosure (LFD). This is classified under CWE-22 (Path Traversal) with a CVSS v3.1 base score of 7.5 (AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N), indicating high severity due to significant confidentiality impact.

Unauthenticated remote attackers can exploit this vulnerability over the network with low attack complexity and no user interaction required. Exploitation allows reading arbitrary files on the affected server, potentially exposing sensitive data such as configuration files or user information.

SiYuan version 3.5.4 addresses the vulnerability. GitHub references detail the issue in kernel/model/file.go (line 1035), vulnerable code in kernel/api/filetree.go (lines 799-886 for v3.4.2), fixing commits (b2274baba2e11c8cf8901b0c5c871e5b27f1f6dd and f8f4b517077b92c90c0d7b51ac11be1b34b273ad), and the reporting issue (#16860). Security practitioners should upgrade to 3.5.4 or later and review the commits for patch details.

OWASP Top 10 for Web (2025)

A01:2025 Broken Access Control

EU & UK References

Vulnerability Data

SiYuan is a personal knowledge management system. In versions prior to 3.5.4, the markdown feature allows unrestricted server side html-rendering which allows arbitrary file read (LFD). Version 3.5.4 fixes the issue.

CWE(s)
CWE-22

Related Threats

MITRE ATT&CK Enterprise Techniques

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-2026-23851Same product: B3Log Siyuan
CVE-2026-33194Same product: B3Log Siyuan
CVE-2026-25992Same product: B3Log Siyuan
CVE-2025-67488Same product: B3Log Siyuan
CVE-2024-55657Same product: B3Log Siyuan
CVE-2024-55658Same product: B3Log Siyuan
CVE-2026-25539Same product: B3Log Siyuan
CVE-2026-33670Same product: B3Log Siyuan
CVE-2026-30869Same product: B3Log Siyuan
CVE-2026-32747Same product: B3Log Siyuan

Affected Assets

b3log
siyuan
≤ 3.5.4

Mitigating Controls

Control response

Prevent
Stop it (NIST 800-53)

—

Detect
Catch it (NIST detect / respond)

—

Harden
Shrink the surface (DISA STIG)

—

Validate
Prove the fix (OWASP ASVS)
  • V5.3.2

Mitigating Controls (NIST 800-53 r5) AI

AC-3 Access Enforcement good match

Enforces the intended directory access authorizations that path traversal would otherwise bypass.

SI-10 Information Input Validation good match

Input validation directly neutralizes special path elements before pathname construction occurs.

AC-6 Least Privilege partial match

Least privilege reduces the impact of any unauthorized file access obtained via traversal.

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-02 partial match
prevents

Patching/maintenance can remediate known path-traversal flaws in deployed software (partial prevention of exploitability) but does nothing to stop the coding defect from being introduced in the first place.

PR.AA-05 none match
prevents

PR.AA-05 defines and reviews access policies but does not address code-level pathname neutralization, so neither direction prevents CWE-22.

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.8.29 Security testing in development and acceptance mostly match
finds

Security testing in development catches path traversal via static/dynamic analysis.

A.8.25 Secure development life cycle partial match
prevents

Secure SDLC mandates input validation and path sanitization that directly prevent path traversal.

A.8.26 Application security requirements partial match
prevents

Application security requirements include rules for safe file handling and canonicalization.

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

Secure architecture principles require least-privilege file access and directory isolation.

A.8.28 Secure coding partial match
prevents

Secure coding standards explicitly forbid unsafe path construction and mandate safe APIs.

A.8.3 Information access restriction partial match
mitigates

Information access restriction limits which files an application may read or write.

References