Raw vector
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:A/VC:H/VI:H/VA:L/SC:N/SI:N/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:XSummary
CVE-2026-34605 is a high-severity Cross-site Scripting (CWE-79) vulnerability in B3Log Siyuan. Its CVSS base score is 8.6 (High).
Operationally, exploitation aligns with the MITRE ATT&CK technique Browser Session Hijacking (T1185); ranked at the 38th percentile by exploit likelihood (below the median); it is not currently listed in the CISA KEV catalog; a public proof-of-concept is referenced.
The strongest mitigations our analysis identified map to SA-11 (Developer Testing and Evaluation) and SI-10 (Information Input Validation) — see the control section below for these in your framework.
Deeper analysis AI-assisted summary
Synthesised by an AI model from the NVD description and linked references — a reading aid, not an authoritative source.
SiYuan is a personal knowledge management system affected by an XSS vulnerability (CWE-79) in versions 3.6.0 through 3.6.1. The SanitizeSVG function added in 3.6.0 to protect the unauthenticated /api/icon/getDynamicIcon endpoint can be bypassed when an attacker supplies namespace-prefixed SVG elements such as <x:script xmlns:x="http://www.w3.org/2000/svg">. Because the Go HTML5 parser records the tag name literally as "x:script", the sanitization check passes the element through; the response is then served with Content-Type image/svg+xml and no Content-Security-Policy header, allowing a browser's XML parser to resolve the namespace and execute the script when the URL is loaded directly.
An unauthenticated remote attacker can exploit the flaw by crafting a malicious icon request that returns executable script in the SVG response. When a victim’s browser renders that response, the attacker can achieve arbitrary JavaScript execution in the victim’s context, resulting in high impact on confidentiality, integrity, and limited availability according to the CVSS 8.6 rating.
The project’s GitHub security advisory and release notes for version 3.6.2 state that the issue has been patched by updating the sanitization logic to handle namespace-prefixed elements correctly.
EPSS for the CVE rose from a low baseline of 0.0016 to a peak of 0.0107, indicating that exploitation interest increased after disclosure.
OWASP Top 10 for Web (2025)
EU & UK References
- 🇪🇺 ENISA EUVD: EUVD-2026-17687
Vulnerability Data
SiYuan is a personal knowledge management system. From version 3.6.0 to before version 3.6.2, the SanitizeSVG function introduced in version 3.6.0 to fix XSS in the unauthenticated /api/icon/getDynamicIcon endpoint can be bypassed by using namespace-prefixed element names such as <x:script…
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xmlns:x="http://www.w3.org/2000/svg">. The Go HTML5 parser records the element's tag as "x:script" rather than "script", so the tag check passes it through. The SVG is served with Content-Type: image/svg+xml and no Content Security Policy; when a browser opens the response directly, its XML parser resolves the prefix to the SVG namespace and executes the embedded script. This issue has been patched in version 3.6.2.
- CWE(s)
Related Threats
MITRE ATT&CK Enterprise Techniques
CVEs Like This One
Affected Assets
Mitigating Controls
Control response
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V1.1.2V1.3.2
Mitigating Controls (NIST 800-53 r5) AI
Developer testing and evaluation can discover missing or incorrect input neutralization through targeted web-application tests.
Input validation directly enforces neutralization of untrusted data before it reaches web output generation.
Output filtering can catch or sanitize unneutralized script content before it is served to users.
Mitigating Controls (NIST CSF 2.0) AI
Derived directly from the weakness types (CWEs) cited in the NVD entry via our AI-authored CWE→CSF cross-walk (authority under review) — links open the control.
Secure SDLC practices directly target introduction of XSS via coding standards/testing (mostly), yet the single broad outcome leaves many specific neutralization vectors unaddressed (partial).
Patching and EOL replacement can remediate known XSS instances in libraries or frameworks (partial) but do nothing to enforce input neutralization in application code (none).
Mitigating Controls (ISO/IEC 27001:2022 Annex A) AI
Derived directly from the weakness types (CWEs) cited in the NVD entry via our AI-authored CWE→ISO cross-walk (authority under review) — links open the control.
Secure-coding testing and automated code-analysis tools are applied to detect improper neutralization of script-related content during web-page generation.
Knowledge exchange on emerging attack techniques and patches reduces the likelihood that cross-site scripting flaws remain unaddressed in deployed applications.
Operational indicators of compromise for web-application attacks can be incorporated into WAF or input-filtering rules, lowering the likelihood that unsanitized data reaches the browser.
Requiring language-specific secure-coding standards and automated scanning during the SDLC catches missing output encoding or improper neutralization of untrusted data before the software reaches production.
Secure-coding standards, SAST scans and removal of insecure code samples together eliminate the failure to neutralize script content that produces cross-site scripting flaws.
Webpage malware scanning and block-listing of known malicious sites reduce the likelihood that reflected or stored script payloads reach a user’s browser.