CVE-2026-84803

high

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.

References

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

Details

Source: Mitre, NVD

Published: 2026-09-02

Updated: 2026-09-02

Risk Information

CVSS v2

Base Score: 9

Vector: CVSS2#AV:N/AC:L/Au:S/C:C/I:C/A:C

Severity: High

CVSS v3

Base Score: 9

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

Severity: Critical

CVSS v4

Base Score: 8.6

Vector: 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

Severity: High

EPSS

EPSS: 0.00234