8.4

CVE-2026-87811: siyuan-note siyuan Cross-site Scripting

CVSS: 8.4v4.0HighDeferred
Published 09-09-2026Last modified 09-09-2026
Open JSON

Vulnerability summary

CVE-2026-87811 is a high (CVSS 8.4) Cross-site Scripting vulnerability in siyuan-note siyuan. EPSS estimates a 0.37% chance of exploitation in the next 30 days, higher than 29.2% of scored vulnerabilities.

Overall risk
34/100
0100
Medium · default modelHow is this calculated?
CVSS score
8.4/10
010
High · v4.0 (CVE.org)
EPSS score
0.37%
0%100%
Low · +0.16 pp in 30 days
KEVNot listedIn no KEV catalog
RansomwareNone recordedNo known use recorded
Public exploits0No public exploits recorded

Timeline

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

Description

SiYuan before v3.8.2 inserts persisted notebook template paths into HTML input value attributes without proper attribute encoding. Attackers can craft malicious template paths that break out of the attribute context and execute JavaScript when a victim opens notebook configuration, enabling same-origin API requests and application state manipulation.

CVSS metrics

4 scores · 2 sources · 2 versions

EPSS trend

Probability

0.37%

Chance of exploitation in the next 30 days

Percentile

29%

Versus all other CVEs

30-day change

+0.16 pp

From 0.21% on 21-09-2026

21-09-202621-10-2026
EPSS score
0.37%

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