CVE-2026-41894

EPSS 0.05%

SiYuan: Path Traversal via Double URL Encoding in `/export/` Endpoint (Incomplete Fix Bypass for CVE-2026-30869)

Published: 4/22/2026Modified: 5/5/2026

Description

### Summary The fix for CVE-2026-30869 in SiYuan v3.5.10 only added a denylist check (`IsSensitivePath`) but did not address the root cause — a redundant `url.PathUnescape()` call in `serveExport()`. An authenticated attacker can use double URL encoding (`%252e%252e`) to traverse directories and read arbitrary workspace files including the full SQLite database (`siyuan.db`), kernel log, and all user documents. ### Details In `kernel/server/serve.go`, the `serveExport()` function (line 314-320) processes file paths as follows: ```go filePath := strings.TrimPrefix(c.Request.URL.Path, "/export/") decodedPath, err := url.PathUnescape(filePath) // second decode fullPath := filepath.Join(exportBaseDir, decodedPath) ``` Go's HTTP server already decodes percent-encoded characters once during request parsing. The additional `url.PathUnescape()` call creates a double-decode vulnerability: 1. Attacker sends: `GET /export/%252e%252e/siyuan.db` 2. Go HTTP decodes `%25` → `%`, result: `URL.Path = /export/%2e%2e/siyuan.db` 3. Go's path cleaner sees `%2e%2e` as literal characters (not `..`), no redirect occurs 4. `url.PathUnescape("%2e%2e")` decodes to `..` 5. `filepath.Join(exportBaseDir, "../siyuan.db")` resolves to `<workspace>/temp/siyuan.db` The CVE-2026-30869 fix added `IsSensitivePath()` which blocks `<workspace>/conf/` and OS-level paths (`/etc`, `/root`, etc.). However, it does NOT block: - `<workspace>/temp/siyuan.db` — full document database - `<workspace>/temp/blocktree.db` — block tree database - `<workspace>/temp/siyuan.log` — kernel log - `<workspace>/temp/asset_content.db` — asset content database Note: the `/appearance/` handler in the same file correctly uses `gulu.File.IsSubPath()` to validate paths (line 447), but this check is missing from the `/export/` handler. ### PoC [poc.zip](https://github.com/user-attachments/files/26866234/poc.zip) Please extract the uploaded compressed file before proceeding 1. docker compose up -d --build 2. sh poc.sh <img width="550" height="184" alt="스크린샷 2026-04-19 오후 5 08 30" src="https://github.com/user-attachments/assets/6aea4334-0b5a-4f45-bd1f-ecfad61ba524" /> ### Impact - Data exfiltration: An authenticated user (including low-privilege Publish/Reader users via the Publish service) can download the entire SQLite document database containing all blocks, documents, attributes, and full-text search indexes. - Information disclosure: Kernel log (`siyuan.log`) leaks internal server paths, versions, configuration details, and error messages.

Affected packages (1)

CVSS scores

SourceVersionSeverityVector
osvCVSS 4.0—CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:H/VI:N/VA:N/SC:N/SI:N/SA:N

References (6)