Vulnerability in Siyuan-Note Siyuan
CVE-2026-100635
SiYuan before v3.8.4 contains an authentication bypass vulnerability in the publish service where session cookies are issued without Secure or SameSite attributes over plaintext HTTP connections. An on-path attacker can observe a valid publish-visitor-session-id cookie from a Basic Auth exchange and replay it to access authenticated publish endpoints without knowing the account password.
Published · last modified .
CVSS v3 metric
CVSS v3 base score 5.9 (Medium). Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:N.
EPSS exploit prediction
No EPSS score from FIRST.org yet. New CVEs usually get one within a few days; no score means no signal yet, not low risk. How EPSS works.
Affected products
Weakness classification (CWE)
References
- github.com/siyuan-note/siyuan/security/advisories/GHSA-7j37-4gq6-wm7m (vendor-advisory)
- github.com/siyuan-note/siyuan/commit/79d47867b106467c951475a9193455b48d1f3682 (patch)
- github.com/siyuan-note/siyuan/commit/ff4d215f78a8d6e6db6052be18b5f9f4db9c7d68 (patch)
- www.vulncheck.com/advisories/siyuan-before-3.8.4-authentication-bypass-via-plai… (third-party-advisory)
Frequently asked questions
- What is CVE-2026-100635?
- CVE-2026-100635 is a medium-severity vulnerability in Siyuan-Note Siyuan, classified under Cleartext Transmission of Sensitive Information. CVSS score: 5.9/10. Published 2026-09-26.
- How severe is CVE-2026-100635?
- Medium severity. CVSS v3 base score is 5.9 out of 10.