Security readout for executives and security teams
Plain-English summary
SiYuan versions before 3.5.4-dev2 can run JavaScript hidden inside an uploaded SVG file when a user views it. This could affect the viewer’s authenticated SiYuan session. The issue requires user interaction and is fixed in 3.5.4-dev2.
Executive priority
Treat as a medium-priority update. The bug is not listed as actively exploited, but it can affect authenticated user sessions if malicious content is viewed.
Technical view
CVE-2026-23645 is a stored XSS issue in SiYuan caused by insufficient sanitization of uploaded SVG files. The CVSS 4.0 score is 5.3. The vector indicates network accessibility, low complexity, no privileges required, and passive user interaction. Impact is limited to downstream confidentiality and integrity effects.
Likely exposure
Exposure applies to SiYuan deployments running versions earlier than 3.5.4-dev2, especially where users can import or upload SVG content from untrusted sources.
Exploitation context
The sources describe exploitation through viewing a malicious uploaded SVG. CISA KEV is not indicated, and the provided sources do not state active exploitation in the wild.
Researcher notes
The advisory maps the issue to CWE-79. Validation should focus on version status and SVG sanitization behavior, without relying on exploit reproduction in production systems.
Mitigation direction
- Upgrade SiYuan to 3.5.4-dev2 or later.
- Restrict or avoid SVG uploads from untrusted sources until upgraded.
- Review vendor advisory and commit details for environment-specific guidance.
Validation and detection
- Inventory SiYuan instances and confirm versions are below or at least 3.5.4-dev2.
- Review upload/import workflows for SVG file handling.
- Check whether untrusted SVG files were added to workspaces before remediation.
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 lookupFile access behavior lookup
The CVE wording references file access or upload behavior, so file telemetry and web shell review may help. This is a Glexia inferred lookup path, not an official MITRE, ATT&CK, or CVE Program mapping.
Open ATT&CK lookupCVE-2026-23645 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
- 5.3 (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:L/SI:L/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:L/SI:L/SA:N——Primary CVE scoreVulnerability scoring details
Base CVSS 4.0 score
5.3MediumVector: CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:P/VC:N/VI:N/VA:N/SC:L/SI:L/SA:N
Source materials
- CVE List V5 sourceCVE List V5
- https://github.com/siyuan-note/siyuan/security/advisories/GHSA-pcjq-j3mq-jv5jCVE reference · x_refsource_CONFIRM
- https://github.com/siyuan-note/siyuan/issues/16844CVE reference · x_refsource_MISC
- https://github.com/siyuan-note/siyuan/commit/11115da3d0de950593ee4ce375cf7f9018484388CVE reference · x_refsource_MISC
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.