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
EPSS: 0.003 (26.1th percentile), scored .
Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 26th percentile — 26.1% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.
EPSS over last 30 days · oldest: 0.003 · newest: 0.003 · change: +0.001
Affected products
Weakness classification (CWE)
References
- GitHub Security Advisory (GHSA-7j37-4gq6-wm7m) (vendor-advisory)
- Patch Commit (patch)
- Patch Commit (patch)
- VulnCheck Advisory: SiYuan before v3.8.4 Authentication Bypass via Plaintext Session Cookie (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.