CVE-2026-59809 SiYuan before v3.8.0 Secret Exfiltration via http_request URL
Attackers can exfiltrate stored secrets by crafting malicious URLs in the http_request MCP tool, exposing sensitive data to external hosts.
- Exploited in the wild
- Not known
- Login needed
- An administrator
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- None listed
What is CVE-2026-59809?
CVE-2026-59809 is a medium-severity vulnerability in siyuan-note siyuan, published on 22 Aug 2026. An attacker needs administrator access to exploit it, with no action from the victim.
Official description
SiYuan before v3.8.0 interpolates secret placeholders into the destination URL parameter of the http_request MCP tool, allowing attackers to exfiltrate stored secrets. An MCP client can craft a request with an attacker-controlled URL containing secret placeholders to send plaintext secret values to any public host without confirmation.
Weakness: CWE-201
Which versions are affected by CVE-2026-59809?
How do I fix CVE-2026-59809?
No fix has been published for CVE-2026-59809 yet. Limit exposure of the affected software until one is available.
Is CVE-2026-59809 being exploited?
There is no known exploitation of CVE-2026-59809 in the wild and no public exploit code.
Sources
Also known as GHSA-27jw-6xjf-hgxj, GHSA-853m-gvvm-6rvx.