XSS in Siyuan-Note Siyuan
CVE-2026-87811
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.
Vulnerability class: XSS (Cross-Site Scripting)
Published · last modified .
CVSS v3 metric
CVSS v3 base score 7.3 (High). Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:U/C:H/I:H/A:N.
EPSS exploit prediction
EPSS: 0.004 (29.3th percentile), scored .
Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 29th percentile — 29.3% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.
EPSS over last 30 days · oldest: 0.004 · newest: 0.004 · change: 0.000
Affected products
Weakness classification (CWE)
References
- github.com/siyuan-note/siyuan/security/advisories/GHSA-v6wf-r2gr-rrgf (vendor-advisory)
- www.vulncheck.com/advisories/siyuan-before-3.8.2-stored-xss-via-notebook-templa… (third-party-advisory)
Frequently asked questions
- What is CVE-2026-87811?
- CVE-2026-87811 is a high-severity vulnerability in Siyuan-Note Siyuan, classified under Cross-site Scripting. CVSS score: 7.3/10. Published 2026-09-09.
- How severe is CVE-2026-87811?
- High severity. CVSS v3 base score is 7.3 out of 10.