Vulnerability · Published Sep 2, 2026 · Assigned by VulnCheck
CVE-2026-84803SiYuan before v3.8.2 Stored XSS via incomplete asset blocklist
Critical 9.0
In plain English
A critical-severity cross-site scripting in siyuan from siyuan-note. Proof-of-concept exploit code is public. The chance it is exploited in the next 30 days is estimated at 0.4% (higher than 37% of all known vulnerabilities).
Severity (CVSS 3.1)9.0Critical
Exploit odds (30 days)0.4%top 62.8% of all CVEs
Exploited in the wildNo reportsCISA SSVC: poc
Attack toolingNoneno public tooling known
Official description
SiYuan before v3.8.2 contains a stored cross-site scripting vulnerability in asset serving due to an incomplete extension blocklist that misses script-capable file types. Attackers can upload files with extensions like .xht, .ehtml, .xsl, .xbl, or .rdf that resolve to executable media types and execute JavaScript to steal API tokens and compromise workspaces.
Affected products (as reported)
| Vendor | Product | Versions |
|---|---|---|
| siyuan-note | siyuan | 0 – before 3.8.2 |
Weakness: CWE-79 · Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:H/I:H/A:H
References
- GitHub Security Advisory (GHSA-7h8j-qw37-w46g) vendor-advisory
- VulnCheck Advisory: SiYuan before v3.8.2 Stored XSS via incomplete asset blocklist third-party-advisory