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SiyuanApplication · B3log

CVE-2026-31809

MEDIUM · 6.1 CVSS v3.1 Published 2026-03-10
Fix available
A fix is available. Upgrade to 3.5.10 or later.
See remediation →
68/100
Remediation priority · Elevated
Public exploit Remotely reachable No privileges

Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.

NVD · unedited
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.

Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.

dbcve analysis
How this class of weakness works · CWE-79

Untrusted input is placed into a web page without being neutralised, so an attacker's markup or script executes in another user's browser. That can hijack sessions, capture keystrokes, or silently perform actions as the victim. Fixing it properly means context-aware output encoding everywhere data meets HTML, backed by a content-security policy as a second line of defence.

General guidance for the cross-site scripting (xss) class — the official description and references above are authoritative for this specific CVE. Want a bespoke review and a reviewed fix? Ask our team →

Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.

NVD · CPE data
SiyuanApplication
Affected:< 3.5.10

CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.

From the vector
Attack vector
Network
Complexity
Low
Privileges
None
User interaction
Required
Scope
Changed
Confidentiality
Low
Integrity
Low
Availability
None

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

Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.

dbcve · scoped
Upgrade available Upgrade to 3.5.10 or later
Fixed in 3.5.10
Recommended fix High confidence

3.5.10

  1. 1. Check your current Siyuan installation version (Help > About)
  2. 2. Download Siyuan version 3.5.10 or later from the official GitHub releases page (github.com/siyuan-note/siyuan/releases)
  3. 3. Backup your Siyuan data (typically in the /data folder of your installation directory)
  4. 4. Install the new version by running the downloaded installer or replacing the existing binaries
  5. 5. Restart the Siyuan application if it was running during the upgrade
  6. 6. Verify the upgrade was successful by checking Help > About shows version 3.5.10 or later
  7. 7. Confirm the vulnerability is fixed by testing that the /api/icon/getDynamicIcon endpoint no longer executes JavaScript from manipulated SVG content

Generated from the published advisory — verify against the referenced sources before acting.

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References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2026-31809 in production — separate from our analysis above.

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What this is

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What belongs here
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  • Version or environment caveats, and links to real fixes
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