Glexia's Take moderate Analyst 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. Prepared Apr 30, 2026, 01:34 UTC (UTC+00:00) Confidence high Sources 3 Public sources used CVE Program CVE List V5 GitHub Security Advisory GHSA-5hc8-qmg8-pw27 Based on public source material and reviewed before publication. Potential ATT&CK relevance 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 · medium confidence lookup 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 lookup cve · low confidence lookup CVE-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 Vulnerability profile CVE Program record Severity Medium CVSS 6.4 (4.0) Known Exploited No Published Mar 10, 2026, 20:56 UTC (UTC+00:00) 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 Official CVE source material 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. 1 CVSS vectors 0 Timeline events 0 ADP providers 2 Source links CVSS vector scores 1 official score We 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. Score Version Severity Vector Exploit Impact Source 6.4 CVSS 4.0 Medium 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 score Vulnerability scoring details CVSS 4.0 Base CVSS 4.0 score 6.4 Medium CVSS 4.0 vector shape for CVE-2026-31807 Attack VectorAttack ComplexityAttack RequirementsPrivileges RequiredUser InteractionVS ConfidentialityVS IntegrityVS AvailabilitySS ConfidentialitySS IntegritySS Availability 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 Attack Vector NetworkAdjacentLocalPhysical Attack Complexity LowHigh Attack Requirements NonePresent Privileges Required NoneLowHigh User Interaction NonePassiveActive VS Confidentiality HighLowNone VS Integrity HighLowNone VS Availability HighLowNone SS Confidentiality HighLowNone SS Integrity HighLowNone SS Availability HighLowNone Source materials CVE List V5 source CVE List V5 https://github.com/siyuan-note/siyuan/security/advisories/GHSA-5hc8-qmg8-pw27 CVE reference · x_refsource_CONFIRM Affected products Products and packages named in the record Vendor Product Version / package Status siyuan-note siyuan < 3.5.10 Listed Weakness CWE details CWE-79 CWE links open conservative ATT&CK lookup hints, not official CWE-to-ATT&CK mappings. Source links are consolidated once in the official source material section above.
cwe · medium confidence lookup 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 lookup
cve · low confidence lookup CVE-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