CVE-2026-87811

8.4 highEPSS 0.4%

High (8.4). EPSS 0.4% chance of exploitation in the next 30 days.

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.

Severity

CVSS 4.0

8.4 high

CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:A/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N

CVSS 3.1

7.3 high

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

EPSS: 0.4% chance of exploitation in the next 30 days; higher than 30% of CVEs (scores of 2026-10-31)
CWE: CWE-79
Published: 2026-09-09
Modified: 2026-09-09
Record from: the NVD, synced 2026-10-19

References

https://github.com/siyuan-note/siyuan/security/advisories/GHSA-v6wf-r2gr-rrgf
https://www.vulncheck.com/advisories/siyuan-before-3.8.2-stored-xss-via-notebook-template-paths

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