Security readout for executives and security teams
Plain-English summary
CVE-2026-31807 affects SiYuan, a personal knowledge management system, before version 3.5.10. An unauthenticated attacker can craft SVG content that bypasses SiYuan’s sanitizer and causes JavaScript to run in a user’s browser if the user interacts with the reflected content. This is a cross-site scripting issue, not a server takeover bug.
Executive priority
Treat as a timely update item for any SiYuan deployment, especially internet-facing or multi-user environments. Business impact is mainly browser-side compromise, such as session or data exposure through XSS, not direct infrastructure compromise. Patch to 3.5.10 should be scheduled promptly.
Technical view
SiYuan’s SanitizeSVG blocked scripts, iframes, foreignObject, event handlers, and javascript: hrefs, but missed SVG animation elements such as animate and set. Those elements can change attributes at runtime, bypassing static sanitization. The issue affects the unauthenticated /api/icon/getDynamicIcon endpoint with type=8 and is a bypass of the CVE-2026-29183 fix.
Likely exposure
Organizations running SiYuan versions earlier than 3.5.10 may be exposed, especially if the SiYuan service is reachable by untrusted users or links can be shared with users. The reported vector is network-accessible and does not require authentication, but successful impact requires user interaction.
Exploitation context
The source bundle reports no CISA KEV listing and provides no evidence of active exploitation. The CVSS vector indicates low attack complexity, no privileges required, and user interaction required. Practical risk is highest where users may open attacker-supplied links or content targeting the vulnerable dynamic icon endpoint.
Researcher notes
This is CWE-79 reflected XSS through an SVG sanitizer bypass. The key issue is runtime mutation by SVG animation elements that were not blocked by SanitizeSVG. Sources state it bypasses the prior CVE-2026-29183 fix in v3.5.9 and is fixed in v3.5.10.
Mitigation direction
- Upgrade SiYuan to version 3.5.10 or later.
- Prioritize externally reachable or shared SiYuan instances.
- Review the GitHub advisory for any vendor-updated guidance.
- Restrict untrusted access to SiYuan until updated, where operationally feasible.
Validation and detection
- Inventory deployed SiYuan versions.
- Confirm all instances are version 3.5.10 or later.
- Check whether SiYuan is reachable from untrusted networks.
- Review logs for unusual requests to /api/icon/getDynamicIcon with type=8.
Public sources used
Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.
Conservative CVE-to-ATT&CK context
These mappings and lookup hints may be relevant to the vulnerability behavior, CWE, affected product, or exposure path. Glexia-inferred context is not an official MITRE, ATT&CK, CWE, or CVE Program mapping.
ATT&CK lookup starting points
Use these exact CWE pages and searches to review the Glexia ATT&CK library from this CVE's weakness and description context.
CWE-79: User-session and phishing behavior lookup
Client-side and session-facing weaknesses should be reviewed alongside initial-access and user-execution behaviors. Open the exact CWE lookup page first, then review the ATT&CK searches from that MITRE weakness context. This is a Glexia lookup hint, not an official ATT&CK mapping.
Open ATT&CK lookupCVE-2026-31807 mapping review
Open the CVE-to-ATT&CK bridge for reviewed, inferred, or future official mappings tied to this CVE.
Open ATT&CK lookup- Severity
- Medium
- CVSS
- 6.4 (4.0)
- Known Exploited
- No
- Published
Vector: 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
CNA and ADP enrichment extracted from CVE v5
These fields come from the CVE record and ADP containers, not from Glexia's Take. They preserve time-varying source decisions such as CISA SSVC, KEV status, CVSS metrics, and provider references.
CVSS vector scores
1 official scoreWe collect every scored CVSS vector available in the official CNA and ADP containers. When more than one version is present, the table keeps the source vectors side by side instead of collapsing them into the highest score.
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——Primary CVE scoreVulnerability scoring details
Base CVSS 4.0 score
6.4MediumVector: 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
Source materials
- CVE List V5 sourceCVE List V5
- https://github.com/siyuan-note/siyuan/security/advisories/GHSA-5hc8-qmg8-pw27CVE reference · x_refsource_CONFIRM
Products and packages named in the record
CWE details
CWE links open Glexia weakness intelligence pages with official CWE context, developer remediation guidance, and related CVE mappings.
Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')
Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting') represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.