CVE-2026-100635: Siyuan-Note Siyuan

Medium severity, CVSS 5.9. EPSS: 0.3% chance of exploitation in the next 30 days.

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.

Affected products

• Siyuan-Note Siyuan: before 3.8.4 (fixed in 3.8.4)

Published 2026-09-26. Last modified 2026-10-08.