CVE-2026-31807
MediumSiYuan has a SVG Sanitizer Bypass via Element — Unauthenticated XSS
Published Mar 10, 2026 · Updated Aug 12, 2026 · Also known as GHSA-5hc8-qmg8-pw27, GO-2026-4667
Key Facts
Routine patching- CVE-2026-31807 is a medium-severity vulnerability (CVSS 6.4 v4) affecting Siyuan (B3log), github.com/siyuan-note/siyuan/kernel (go).
- It is not listed in any known-exploited vulnerabilities catalog. No public exploit code is known.
- EPSS estimates a 0.5% probability of exploitation in the next 30 days.
- Fixed versions are available, including Siyuan 3.5.10, github.com/siyuan-note/siyuan/kernel 0.0.0-20260310025236-297bd526708f.
- Brandefense priority: routine patching, as no exploitation is known and its severity is moderate or low.
CVSS v4
6.4
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:P/VC:N/VI:N/VA:N/SC:H/SI:H/SA:N/E:X/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 (30-day exploit likelihood)
0.5%
Higher than 41.5% of all scored CVEs
Exploited in the wild
No known
Not in a known-exploited catalog
Public exploit code
None known
Get the full CVE-2026-31807 brief as a PDF
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Description
SiYuan is a personal knowledge management system. Prior to 3.5.10, SiYuan's SVG sanitizer (SanitizeSVG) blocks dangerous elements (, , ) and removes on* event handlers and javascript: in href attributes. However, it does NOT block SVG animation elements (, ) which can dynamically set attributes to dangerous values at runtime, bypassing the static sanitization. This allows an attacker to inject executable JavaScript into the unauthenticated /api/icon/getDynamicIcon endpoint (type=8), creating a reflected XSS. This is a bypass of the fix for CVE-2026-29183 (fixed in v3.5.9). This vulnerability is fixed in v3.5.10.
Affected Products
3 affected entries in total| Product | Affected versions | Fixed in |
|---|---|---|
| SiyuanB3log | >= < 3.5.10 | 3.5.10 |
| github.com/siyuan-note/siyuan/kernelgo | See advisory | 0.0.0-20260310025236-297bd526708f |
Patched Releases
Siyuan
3.5.10
github.com/siyuan-note/siyuan/kernel
0.0.0-20260310025236-297bd526708f
Timeline
Publicly disclosed
Mar 10, 2026
Last updated
Aug 12, 2026
Weakness Type
- CWE-79 Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')
References
- advisoryGHSA advisory
- advisoryhttps://github.com/CVEProject/cvelistV5/tree/main/cves/2026/31xxx/CVE-2026-31807.json
- advisoryhttps://nvd.nist.gov/vuln/detail/CVE-2026-31807
- articlehttps://github.com/siyuan-note/siyuan/releases/tag/v3.5.10
- articlehttps://github.com/siyuan-note/siyuan/security/advisories/GHSA-5hc8-qmg8-pw27
FAQ
Common Questions.
SiYuan is a personal knowledge management system.
Affected: Siyuan (B3log) versions >= < 3.5.10; github.com/siyuan-note/siyuan/kernel (go). The full list is in the CVE brief.
It is not listed in any known-exploited vulnerabilities catalog.
No, it is not currently listed in the CISA Known Exploited Vulnerabilities catalog.
No public exploit code is known.
Fixed versions are available, including Siyuan 3.5.10, github.com/siyuan-note/siyuan/kernel 0.0.0-20260310025236-297bd526708f.
Brandefense priority: routine patching, as no exploitation is known and its severity is moderate or low.
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