Stored Cross-Site Scripting Vulnerability in SiYuan by SiYuan
CVE-2026-84803

8.6HIGH

Key Information:

Vendor

Siyuan-note

Status
Siyuan
Vendor
CVE Published:
2 September 2026

What is CVE-2026-84803?

SiYuan prior to version 3.8.2 has a vulnerability that allows stored cross-site scripting due to an insufficient blocklist for file extensions. This allows attackers to upload malicious files with extensions such as .xht, .ehtml, .xsl, .xbl, or .rdf. These files can lead to the execution of JavaScript, which may be leveraged to capture sensitive API tokens and potentially compromise workspaces.

Affected Version(s)

siyuan 0 < 3.8.2

siyuan 3.8.2

References

https://github.com/siyuan-note/siyuan/security/advisories...
vendor-advisory
https://www.vulncheck.com/advisories/siyuan-before-3.8.2-...
third-party-advisory

CVSS V4

Score:
8.6
Severity:
HIGH
Confidentiality:
High
Integrity:
High
Availability:
High
Attack Vector:
Network
Attack Complexity:
Low
Attack Required:
None
Privileges Required:
Undefined
User Interaction:
Unknown

Timeline

  • Vulnerability published

  • Vulnerability Reserved

Credit

Akokonunes
.