CVE-2026-126776

Description

SiYuan 3.7.0 before 3.8.10 on Windows contains a path traversal vulnerability in kernel/util/webfetch.go that allows attackers to write files outside the import directory via backslash-encoded filenames. Attackers controlling a URL fetched by the MCP web_fetch or http_request tools can use %5C-encoded ..\ sequences to write chosen response bytes to directories above temp/import that are writable by the SiYuan user.

References

• https://github.com/siyuan-note/siyuan/blob/v3.7.0/kernel/util/webfetch.go#L155
• https://github.com/siyuan-note/siyuan/commit/94d6a42a0362c0a6938a29ab84addb1fe0aca21c
• https://github.com/siyuan-note/siyuan/releases/tag/v3.8.10
• https://github.com/siyuan-note/siyuan/security/advisories/GHSA-hq2c-hh95-vrr6
• https://www.vulncheck.com/advisories/siyuan-3.7.0-before-3.8.10-path-traversal-file-write-via-mcp-web-fetch