CVE-2026-33203 SiYuan has an Unauthenticated WebSocket DoS via Auth Keepalive Bypass
Remote attackers can crash the SiYuan kernel via unauthenticated WebSocket messages, causing denial of service.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-33203?
CVE-2026-33203 is a high-severity denial of service vulnerability in B3log Siyuan, published on 20 Mar 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official description
SiYuan is a personal knowledge management system. Prior to version 3.6.2, the SiYuan kernel WebSocket server accepts unauthenticated connections when a specific "auth keepalive" query parameter is present. After connection, incoming messages are parsed using unchecked type assertions on attacker-controlled JSON. A remote attacker can send malformed messages that trigger a runtime panic, potentially crashing the kernel process and causing denial of service. Version 3.6.2 fixes the issue.
Which versions are affected by CVE-2026-33203?
3 open source packages ship an affected version, including github.com/siyuan-note/siyuan/kernel. It affects 1 product.
| Package | Affected | Fixed in |
|---|---|---|
github.com/siyuan-note/siyuan/kernel Go | All versions | None |
github.com/siyuan-note/siyuan/kernel Go | All versions | 3.6.2 |
github.com/siyuan-note/siyuan/kernel Go | All versions | 3.6.2 |
Products include B3log Siyuan.
How do I fix CVE-2026-33203?
Upgrade github.com/siyuan-note/siyuan/kernel to 3.6.2 or later.
Upgrade, then put limits on request size, rate and nesting depth so one client cannot exhaust the service. More about Denial of service.
Is CVE-2026-33203 being exploited?
It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-33203 exists.
Other vulnerabilities in B3log Siyuan
- CVE-2026-32938 SiYuan has an Arbitrary File Read in its Desktop Publish Service
- CVE-2026-33669 SiYuan has Arbitrary Document Reading within the Publishing Service
- CVE-2026-33670 SiYuan has directory traversal within its publishing service
- CVE-2026-32767 SiYuan: Authorization Bypass Allows Arbitrary SQL Execution via Search API
- CVE-2024-53504 SQL injection in n/a
Sources
Also known as GHSA-3g9h-9hp4-654v, GO-2026-4752.