Critical severity · published Sep 2, 2026
CVE-2026-84803
SiYuan before v3.8.2 Stored XSS via incomplete asset blocklist
9.0
CVSS
0.4%
EPSS
No
On KEV
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.
CVSS vector
CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:H/I:H/A:H
Attack vector
Network
Complexity
Low
Privileges
Low
User interaction
Required
Confidentiality
High
Integrity
High
Availability
High
Scope
Changed
Exploitation
Is it being used?
Exploit prediction (EPSS)0.4% · higher than 37% of CVEs
Exploited in the wildNo evidence yet
CISA KEVNot listed
Ransomware campaign useNot known
Affected products
Which versions
SI
siyuan · siyuan-note
before 3.8.2 · source: vendor
References
NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-84803
CVE.org
https://www.cve.org/CVERecord?id=CVE-2026-84803
github.com
https://github.com/siyuan-note/siyuan/security/advisories/GHSA-7h8j-qw37-w46g
www.vulncheck.com
https://www.vulncheck.com/advisories/siyuan-before-3.8.2-stored-xss-via-incomplete-asset-blocklist
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