CVE-2026-84803 PUBLISHED

SiYuan before v3.8.2 Stored XSS via incomplete asset blocklist

Assigner: VulnCheck
Reserved: 02.09.2026 Published: 02.09.2026 Updated: 02.09.2026

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: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 Score: 8.6

Exploitability Metrics		Vulnerable System Impact Metrics		Subsequent System Impact Metrics
Attack Vector	Network	Confidentiality	High	Confidentiality	None
Attack Complexity	Low	Integrity	High	Integrity	None
Attack Requirements	None	Availability	High	Availability	None
Privileges Required	Low
User Interaction	Passive

CVSS 4.0

CVSS Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:H/I:H/A:H
CVSS Score: 9

Attack Vector	Network	Scope	Changed
Attack Complexity	Low	Confidentiality Impact	High
Privileges Required	Low	Integrity Impact	High
User Interaction	Required	Availability Impact	High

CVSS 3.1

Product Status

Vendor	siyuan-note
Product	siyuan
Versions	Default: unaffected affected from 0 to 3.8.2 (excl.) Version 3.8.2 is unaffected

Credits

Akokonunes reporter

References

Problem Types

Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting') CWE