CVE-2026-34523

A path traversal vulnerability in the static file route handler allows any unauthenticated user to determine whether files exist anywhere on the server's filesystem. By sending percent-encoded ../ sequences (%2E%2E%2F) in requests to static file routes, an attacker can check for the existence of files (404 if it doesn't exist, 403 means it exists).

Details

The vulnerability is in createRouteHandler (src/users.js:947–963), which backs all user-data static file routes:

function createRouteHandler(directoryFn) {
    return async (req, res) => {
        const directory = directoryFn(req);
        const filePath = decodeURIComponent(req.params[0]);
        const exists = fs.existsSync(path.join(directory, filePath)); // no boundary check here
        if (!exists) {
            return res.sendStatus(404);
        }
        return res.sendFile(filePath, { root: directory });
    };
}

req.params[0] contains the raw (percent-encoded) wildcard from the URL. After decodeURIComponent, a request path like /characters/%2E%2E%2F%2E%2E%2FUsers/kirakira decodes to ../../Users/kirakira, and path.join resolves it outside the intended directory. res.sendFile correctly blocks the file from being served (the send module's root check returns 403), but fs.existsSync had already run, and the 403/404 distinction reveals the result.

Affected routes (they all use the same handler, so they're all affected):

• /characters/*
• /user/files/*
• /assets/*
• /user/images/*
• /backgrounds/*
• /User%20Avatars/*

PoC

curl -o /dev/null -s -w "%{http_code}\n" "http://localhost:8000/characters/%2E%2E%2F%2E%2E%2F%2E%2E%2F%2E%2E%2F%2E%2E%2F%2E%2E%2F%2E%2E%2FUsers/kirakira/something"

Resolution

The issue was addressed in version 1.17.0.

While file contents cannot be read (the send module blocks actual delivery), anyone who can reach the SillyTavern HTTP port can check the existence of files on the host filesystem.

Input manipulates file paths to reach files outside the intended directory, such as configuration or credential files. Typical impact: unauthorized file read or write outside the intended directory.

CVE-2026-34523 has a CVSS score of 5.3 (Medium). The vector is network-reachable, no privileges required, and no user interaction. A CVSS score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether this affects your application depends on whether the vulnerable code is present and reachable in your environment. A fixed version is available (1.17.0); upgrading removes the vulnerable code path.

Kodem intelligence

1. What is CVE-2026-34523? CVE-2026-34523 is a medium-severity path traversal vulnerability in sillytavern (npm), affecting versions <= 1.16.0. It is fixed in 1.17.0. Input manipulates file paths to reach files outside the intended directory, such as configuration or credential files.
2. How severe is CVE-2026-34523? CVE-2026-34523 has a CVSS score of 5.3 (Medium). This score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether it represents real risk in your environment depends on whether the vulnerable code is present and reachable.
3. Which versions of sillytavern are affected by CVE-2026-34523? sillytavern (npm) versions <= 1.16.0 is affected.
4. Is there a fix for CVE-2026-34523? Yes. CVE-2026-34523 is fixed in 1.17.0. Upgrade to this version or later.
5. Is CVE-2026-34523 exploitable, and should I be worried? Whether CVE-2026-34523 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
6. What actually determines whether CVE-2026-34523 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
7. How do I fix CVE-2026-34523? Upgrade sillytavern to 1.17.0 or later.