CVE-2026-84803CWE-79cross-site-scripting

CVE-2026-84803

Critical · published September 2, 2026

CVSS v3.1
9.0
EPSS
0%
Percentile
36.0
In the wild
Unconfirmed
What it is

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.

The record
Technical detail
CVSS v3.1
9.0 · CRITICAL
Vector
CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:H/I:H/A:H
CVSS v4.0
8.6 · 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
EPSS
0.00428 · 36.0th percentile
Weakness
CWE-79 · Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')
Published
2026-09-02T16:17Z
References (3)
https://github.com/siyuan-note/siyuan/security/advisories/GHSA-7h8j-qw37-w46g · [email protected]https://www.vulncheck.com/advisories/siyuan-before-3.8.2-stored-xss-via-incomplete-asset-blocklist · [email protected]https://github.com/siyuan-note/siyuan/security/advisories/GHSA-7h8j-qw37-w46g · 134c704f-9b21-4f2e-91b3-4a467353bcc0
EPSS history
Timeline
  • 04 SEP 03:44Z
    EPSS moved — → 0%
    epss
  • 02 SEP 11:11Z
    SiYuan before v3.8.2 Stored XSS via incomplete asset blocklist
    cvelistv5