9

CVE-2026-84803: siyuan-note siyuan Cross-site Scripting

CVSS: 9.0v3.1CriticalDeferred
Published 02-09-2026Last modified 02-09-2026
Open JSON

Vulnerability summary

CVE-2026-84803 is a critical (CVSS 9.0) Cross-site Scripting vulnerability in siyuan-note siyuan. EPSS estimates a 0.43% chance of exploitation in the next 30 days, higher than 35.9% of scored vulnerabilities.

Overall risk
70/100
0100
High · default modelHow is this calculated?
CVSS score
9.0/10
010
Critical · v3.1 (CVE.org)
EPSS score
0.43%
0%100%
Low · +0.19 pp in 30 days
KEVNot listedIn no KEV catalog
RansomwareNone recordedNo known use recorded
Public exploits0No public exploits recorded

Timeline

  1. 02-09-2026
    PublishedVulnerability first disclosed.
  2. 02-09-2026
    Last modifiedVulnerability information updated.

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 metrics

4 scores · 2 sources · 2 versions

EPSS trend

Probability

0.43%

Chance of exploitation in the next 30 days

Percentile

36%

Versus all other CVEs

30-day change

+0.19 pp

From 0.23% on 21-09-2026

21-09-202621-10-2026
EPSS score
0.43%

Known exploited

Compare KEV catalogs

Not in any of the 3 tracked catalogs.

Public exploits

0 found

No public exploits indexed.

Weaknesses

CWE · root cause

Affected systems

Siyuan-note1 product

1 vendor · 1 product

References

2 links