What is the CVSS score of CVE-2026-31809?

CVE-2026-31809 has a CVSS 3.1 base score of 6.1 (Medium). CVSS vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N. EPSS exploitation probability: 0.0%.

Which versions of Siyuan are affected by CVE-2026-31809?

Organizations using SiYuan should be aware of moderate risk from CVE-2026-31809, a cross-site scripting vulnerability rated CVSS 6.1.. A patch is available.

Is there a public PoC exploit available for CVE-2026-31809?

Yes, a public proof-of-concept exploit is available for CVE-2026-31809. Prioritise patching immediately. EPSS: 0.0%.

How to fix or mitigate CVE-2026-31809?

Within 30 days: Identify affected systems and apply vendor patches as part of regular patch cycle. Verify Content-Security-Policy and output encoding.

Siyuan CVE-2026-31809

MEDIUM

Cross-site Scripting (XSS) (CWE-79)

2026-03-10 security-advisories@github.com

GHSA-pmc9-f5qr-2pcr

XSS Siyuan Suse

6.1

CVSS 3.1 · GitHub Advisory

Severity by source

GitHub Advisory PRIMARY

6.1 MEDIUM

AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N

SUSE

MEDIUM

qualitative

Primary rating from GitHub Advisory.

CVSS VectorGitHub Advisory

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

Attack Vector

Network

Attack Complexity

Low

Privileges Required

None

User Interaction

Required

Scope

Changed

Confidentiality

Low

Integrity

Low

Availability

None

Lifecycle Timeline

Patch released

Mar 31, 2026 - 21:13 nvd

Patch available

Analysis Generated

Mar 12, 2026 - 21:55 vuln.today

PoC Detected

Mar 11, 2026 - 20:16 vuln.today

Public exploit code

CVE Published

Mar 10, 2026 - 21:16 nvd

MEDIUM 6.1

DescriptionGitHub Advisory

SiYuan is a personal knowledge management system. Prior to 3.5.10, SiYuan's SVG sanitizer (SanitizeSVG) checks href attributes for the javascript: prefix using strings.HasPrefix(). However, inserting ASCII tab (	), newline (
), or carriage return () characters inside the javascript: string bypasses this prefix check. Browsers strip these characters per the WHATWG URL specification before parsing the URL scheme, so the JavaScript still executes. This allows an attacker to inject executable JavaScript into the unauthenticated /api/icon/getDynamicIcon endpoint, creating a reflected XSS. This is a second bypass of the fix for CVE-2026-29183 (fixed in v3.5.9). This vulnerability is fixed in 3.5.10.

AnalysisAI

SiYuan's SVG sanitizer fails to properly filter malicious href attributes when whitespace characters are inserted into javascript: URLs, allowing reflected cross-site scripting on the unauthenticated /api/icon/getDynamicIcon endpoint. Public exploit code exists for this vulnerability, which bypasses the previous fix for CVE-2026-29183. Attackers can inject executable JavaScript to target unauthenticated users of SiYuan versions prior to 3.5.10.

Technical ContextAI

Classified as CWE-79 (Cross-site Scripting (XSS)). Affects Siyuan. SiYuan is a personal knowledge management system. Prior to 3.5.10, SiYuan's SVG sanitizer (SanitizeSVG) checks href attributes for the javascript: prefix using strings.HasPrefix(). However, inserting ASCII tab (	), newline (
), or carriage return () characters inside the javascript: string bypasses this prefix check. Browsers strip these characters per the WHATWG URL specification before parsing the URL scheme, so the JavaScript still executes. This allows an attacker to inject execu

RemediationAI

Fixed in version 3.5.10.. Implement output encoding and Content Security Policy headers. Restrict network access to the affected service where possible.