CVE-2026-100635 SiYuan before v3.8.4 Authentication Bypass via Plaintext Session Cookie
An on-path attacker can steal session cookies over HTTP to bypass authentication and access protected publish endpoints in SiYuan.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- None listed
What is CVE-2026-100635?
CVE-2026-100635 is a high-severity authentication bypass vulnerability in siyuan-note siyuan, published on 26 Sep 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official description
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.
Weakness: CWE-319
Which versions are affected by CVE-2026-100635?
How do I fix CVE-2026-100635?
No fix has been published for CVE-2026-100635 yet. Limit exposure of the affected software until one is available.
Upgrade, and rotate credentials and sessions that may have been exposed. More about Authentication bypass.
Is CVE-2026-100635 being exploited?
It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-100635 exists.
Sources
Also known as GHSA-7j37-4gq6-wm7m, GHSA-9f49-xx3h-chx9.