CVE-2026-67918: Hermes Studio Path Traversal Vulnerability

CVE-2026-67918 Overview

CVE-2026-67918 is a directory traversal vulnerability [CWE-22] in hermes-studio version 0.6.26. The flaw resides in the validatePath function used by the api/hermes/download endpoint. A remote, unauthenticated attacker can supply crafted path input to read arbitrary files from the server file system. Successful exploitation exposes sensitive information stored outside the intended download directory.

Critical Impact
Unauthenticated remote attackers can retrieve arbitrary files from the host running hermes-studio, including configuration files, credentials, and application source code.

Affected Products

hermes-studio version 0.6.26

Discovery Timeline

2026-08-17 - CVE-2026-67918 published to the National Vulnerability Database (NVD)
2026-08-18 - Last updated in NVD database

Technical Details for CVE-2026-67918

Vulnerability Analysis

The vulnerability exists in the validatePath function that is intended to sanitize user-supplied file path input before passing it to the download handler. The validation logic fails to properly canonicalize the requested path, allowing traversal sequences to bypass the check. An attacker can send a request to api/hermes/download containing directory traversal characters and reach files outside the designated download root.

Because the endpoint does not require authentication, exploitation is trivial. The impact is limited to confidentiality; the flaw does not permit modifying files or degrading service availability. Attackers commonly target application configuration files, environment files, and operating system files that store credentials or tokens.

Root Cause

The root cause is improper limitation of a pathname to a restricted directory [CWE-22]. The validatePath function does not fully resolve symbolic sequences such as ../ before comparing the path against an allow list. Any control character or encoded traversal sequence that survives normalization is later resolved by the file system, letting the request escape the intended directory boundary.

Attack Vector

Exploitation occurs over the network against the api/hermes/download endpoint. An attacker issues an HTTP request supplying a manipulated file path parameter containing traversal sequences. The server processes the request through the flawed validatePath routine and returns the contents of the referenced file. No user interaction, privileges, or prior access is required. See the GitHub PoC Repository for a working proof of concept.

No verified code sample is available for republication. Refer to the linked proof of concept for the exact request structure used to trigger the flaw.

Detection Methods for CVE-2026-67918

Indicators of Compromise

HTTP requests to the api/hermes/download endpoint containing ../, ..\, or URL-encoded equivalents such as %2e%2e%2f in path parameters.
Access log entries showing downloads of files outside the expected media or asset directories, including /etc/passwd, .env files, or application configuration files.
Anomalous file access patterns from the hermes-studio service process reading files outside its normal working directory.

Detection Strategies

Deploy web application firewall (WAF) rules that inspect and block traversal sequences in query parameters and request bodies destined for api/hermes/download.
Correlate outbound response sizes and content types from the download endpoint against expected asset baselines to surface anomalous file retrievals.
Hunt for successful HTTP 200 responses to the download endpoint paired with request paths containing traversal patterns or unusual file extensions.

Monitoring Recommendations

Enable verbose access logging on the hermes-studio API and forward logs to a centralized analytics platform for retention and searchability.
Alert on repeated 200-status responses returning file content from paths outside the configured asset directory.
Track process-level file open events on the hermes-studio host to identify reads of sensitive files such as /etc/shadow, SSH keys, and cloud credential files.

How to Mitigate CVE-2026-67918

Immediate Actions Required

Restrict network exposure of the hermes-studio api/hermes/download endpoint to trusted networks or place it behind an authenticated reverse proxy.
Deploy WAF rules that reject requests containing directory traversal sequences before they reach the application.
Review access logs for prior exploitation attempts and rotate any credentials that may have been readable through the download endpoint.

Patch Information

At the time of NVD publication, no vendor advisory or fixed release has been referenced. Monitor the hermes-studio project repository for an update beyond version 0.6.26 that revises the validatePath function. Refer to the GitHub PoC Repository for technical context while awaiting a vendor patch.

Workarounds

Run hermes-studio as a low-privilege user with file system access restricted to its asset directory using operating system controls such as chroot, containers, or mandatory access control policies.
Add a reverse proxy rule that strips or rejects request paths containing .., %2e%2e, or backslash sequences before forwarding to hermes-studio.
Disable or firewall the download endpoint entirely if it is not required for operational workflows.

bash

# Example nginx rule to block traversal sequences reaching hermes-studio
location /api/hermes/download {
    if ($request_uri ~* "(\.\./|\.\.\\|%2e%2e%2f|%2e%2e/)") {
        return 403;
    }
    proxy_pass http://hermes_studio_backend;
}