GHSA-rxjr-6c9q-h67x: Path Traversal
Summary
@logto/tunnel serves custom sign-in experience files from the --experience-path directory. When the tunnel service is reachable, a requester can use ../ path segments in a static asset request to read files outside that directory that the CLI process can read.
Details
The tunnel command accepts --experience-path as the local folder path for custom sign-in experience assets. packages/tunnel/src/commands/tunnel/index.ts enables createStaticFileProxy(path) when that option is set and sends non-Logto, non---experience-uri requests to that static proxy. The server is started with server.listen(port).
packages/tunnel/src/commands/tunnel/utils.ts builds the filesystem path as path.join(staticPath, fallBackToIndex ? index : request.url). For file asset paths, request.url is used directly. A request URL such as /../secret.txt resolves outside staticPath and is then opened with fs.open(requestPath, 'r'). There is no URL normalization and no containment check that the resolved path remains under the configured static directory before the file is read and returned.
The proof boundary is the packaged CLI end-to-end run. The filesystem read primitive was validated with equivalent Node HTTP handling for the affected code path, including that Node preserves /../secret.txt in request.url and that bare server.listen(port) binds to all interfaces on this platform.
PoC
1. Create a custom UI directory at /tmp/logto-ui/static with /tmp/logto-ui/static/index.html. 2. Create a sibling file outside the static root, for example /tmp/logto-ui/secret.txt. 3. Start the tunnel with logto-tunnel --endpoint https://<tenant-id>.logto.app --port 9000 --experience-path /tmp/logto-ui/static. 4. Request http://<host>:9000/../secret.txt. 5. The response body contains the contents of /tmp/logto-ui/secret.txt.
Impact
The observed result is arbitrary file read outside the configured custom UI static directory. If the tunnel port is reachable from another host, an unauthenticated network peer can read local files readable by the logto-tunnel process, including development secrets or credentials stored near the custom UI project.
Affected Software
Remediation
Recommended actions to resolve this vulnerability, in priority order.
- Upgrade
Upgrade
npm/@logto/tunnelto a version that resolves this vulnerability.Fixed in 0.3.9 - Configuration
Set logto-tunnel --experience-path to a directory containing only the static assets you want to be served, and ensure no sensitive files (e.g., secrets/credentials) are present in the same parent directories or readable by the logto-tunnel process.
logto-tunnel (custom sign-in experience static proxy) --experience-path = /tmp/logto-ui/static (or another directory you control) - Compensating control
Restrict network access to the tunnel port (--port 9000 in the example) so it is not reachable from other hosts/peers that can send unauthenticated requests for static assets (e.g., allow only trusted source IPs/management networks at the firewall/ACL).
Event History
Frequently Asked Questions
Which deployments are exposed?
Deployments running the tunnel command with --experience-path configured are exposed when the tunnel service is reachable by a requester. The static file proxy is enabled when that option is set.
What does an attacker need to exploit this issue?
An attacker needs to be able to send requests to the reachable tunnel service and request a static asset path containing ../ segments. They can read only files that are accessible to the CLI process.
Is the tunnel affected when no custom experience path is configured?
The described static file proxy is enabled only when --experience-path is set. The provided information does not indicate exposure through this path when that option is not configured.