CVE-2026-84803

8.6 highEPSS 0.4%

High (8.6). EPSS 0.4% chance of exploitation in the next 30 days.

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.

Severity

CVSS 4.0

8.6 high

CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:P/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N

CVSS 3.1

9.0 critical

CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:H/I:H/A:H

EPSS: 0.4% chance of exploitation in the next 30 days; higher than 37% of CVEs (scores of 2026-10-31)
CWE: CWE-79
Published: 2026-09-02
Modified: 2026-09-02
Record from: the NVD, synced 2026-10-19

References

https://github.com/siyuan-note/siyuan/security/advisories/GHSA-7h8j-qw37-w46g
https://www.vulncheck.com/advisories/siyuan-before-3.8.2-stored-xss-via-incomplete-asset-blocklist
https://github.com/siyuan-note/siyuan/security/advisories/GHSA-7h8j-qw37-w46g

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