# CVE-2026-109309: SiYuan kernel plugin HTTP server absolute path traversal

Source: https://junglewise.ai/threats/cve-2026-109309-siyuan-v3-7-0-before-v3-8-6-contains-an-absolute-path-traversal  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-10-12. Updated: 2026-10-16  
License: CC BY 4.0 with a link back

CVE-2026-109309 · Severity: medium · CVSS 6.5 · Published 2026-10-12

SiYuan is a note-taking application with a plugin system that includes a private HTTP server for kernel plugins. Versions 3.7.0 through 3.8.5 contain a vulnerability where a malicious plugin can read arbitrary files from the host system that the SiYuan process can access, including API tokens and configuration files. An attacker who can load a compromised plugin gains immediate unauthorized file access.

Technologies: [SiYuan](https://junglewise.ai/threats/technologies/siyuan). Vendors: [SiYuan](https://junglewise.ai/threats/vendors/siyuan).

## Quick answers

**Is CVE-2026-109309 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-109309 being exploited in the wild.

**How severe is CVE-2026-109309?** Medium severity, with a CVSS score of 6.5, published 12 October 2026.

**Which products and versions are affected?** SiYuan 3.7.0 through 3.8.5.

**Is there a fix for CVE-2026-109309?** Yes: fixed in 3.8.6. Until then: Disable untrusted kernel plugins; configure bazaar.trust to false in conf.json to prevent automatic plugin loading; restrict API token access through environment variables or credential management systems. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**How is CVE-2026-109309 attacked?** It is in a software library.

**Am I affected by CVE-2026-109309?** Check whether you run SiYuan at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## How to fix

- Fixed in 3.8.6

Disable untrusted kernel plugins; configure bazaar.trust to false in conf.json to prevent automatic plugin loading; restrict API token access through environment variables or credential management systems.

## Technical details

The vulnerability is an absolute path traversal in the kernel plugin private HTTP server dispatcher (kernel/plugin/service_contract.go). A kernel plugin handler can return ResponseFile.Path with an absolute file path, which is passed directly to gin.Context.File() without validation, path canonicalization, symlink checks, or allow-listing. The kernel plugin system runs with administrator privileges (RoleAdministrator JWT), and the /plugin/private/:name/*path route is only gated by authentication checks that default to admin role for localhost connections when accessAuthCode is empty. A plugin can exploit Object.seal() behavior in the JavaScript sandbox to mutate the http handler and serve arbitrary files.

## Affected products

- SiYuan SiYuan 3.7.0 through 3.8.5

## Timeline

- 2026-09-24: disclosed
- 2026-10-12: advisory

## References

- [https://github.com/siyuan-note/siyuan/commit/c6494375ea40ee973f430f0e85d50f1862a30d81](https://github.com/siyuan-note/siyuan/commit/c6494375ea40ee973f430f0e85d50f1862a30d81)
- [https://github.com/siyuan-note/siyuan/security/advisories/GHSA-phmw-4rgv-r4xv](https://github.com/siyuan-note/siyuan/security/advisories/GHSA-phmw-4rgv-r4xv)

## Related threats

- [SiYuan path traversal in web fetch](https://junglewise.ai/threats/cve-2026-126776-siyuan-3-7-0-before-3-8-10-on-windows-contains-a-path-traversal)
- [SiYuan publish filter information disclosure in local storage](https://junglewise.ai/threats/go-2026-6836-siyuan-the-publish-filter-for-local-storage-returns-the-7f022e62)
- [SiYuan path traversal via GLOBALROOT alias bypass](https://junglewise.ai/threats/cve-2026-118680-siyuan-3-8-7-through-3-8-8-fails-to-normalize-windows-globalroot)
- [SiYuan SQL injection in history search](https://junglewise.ai/threats/cve-2026-116170-siyuan-before-v3-8-7-contains-an-sql-injection-vulnerability)
- [SiYuan cross-site scripting in /check-auth redirect](https://junglewise.ai/threats/cve-2026-116167-siyuan-from-2-9-0-before-3-8-7-contains-a-cross-site-scripting)