CVE-2024-34470: Mailinspector Path Traversal Vulnerability

CVE-2024-34470 Overview

CVE-2024-34470 is an unauthenticated path traversal vulnerability in HSC Mailinspector versions 5.2.17-3 through 5.2.18. The flaw resides in /public/loader.php, where the path parameter fails to validate whether the requested file or directory is contained within the webroot. Remote attackers can supply traversal sequences to read arbitrary files from the underlying server, including configuration files, credentials, and other sensitive data. No authentication or user interaction is required to exploit this issue. The vulnerability is tracked under CWE-29: Path Traversal: ..\filename.

Critical Impact

Remote unauthenticated attackers can read arbitrary files on Mailinspector servers, exposing credentials and configuration data. The EPSS score of 93.549% places this vulnerability in the top 1% most likely to be exploited.

Affected Products

• HSC Mailinspector 5.2.17-3
• HSC Mailinspector 5.2.18
• All intermediate versions between 5.2.17-3 and 5.2.18

Discovery Timeline

• 2024-05-06 - CVE-2024-34470 published to NVD
• 2025-06-17 - Last updated in NVD database

Technical Details for CVE-2024-34470

Vulnerability Analysis

The vulnerability exists in the file-loading routine of /public/loader.php. The script accepts a path parameter from HTTP requests and uses its value to open and return file contents. The implementation does not normalize the path or verify that the resolved file resides within the application's webroot directory. Attackers can submit sequences such as ../../../../etc/passwd to traverse out of the intended directory and access any file readable by the web server process. Because the endpoint is exposed without authentication, exploitation requires only network access to the Mailinspector web interface.

Root Cause

The root cause is missing input validation and path canonicalization in the loader.php handler. The application trusts the user-supplied path value directly when invoking file read operations. There is no allowlist of permitted directories, no rejection of traversal sequences such as .., and no check that the canonical path remains inside the webroot. This pattern matches [CWE-29], where Windows or Unix-style relative path components bypass intended access boundaries.

Attack Vector

An attacker sends a single HTTP request to the vulnerable endpoint with a crafted path parameter. For example, a request resembling GET /public/loader.php?path=../../../../etc/passwd returns the contents of the targeted file in the HTTP response. Attackers typically use this primitive to harvest configuration files, database credentials, private keys, and session data. Disclosed credentials often enable follow-on attacks such as authenticated access, lateral movement, or full system compromise. A proof-of-concept is published in the public PoC repository.

Detection Methods for CVE-2024-34470

Indicators of Compromise

• HTTP requests to /public/loader.php containing ../ or URL-encoded variants such as %2e%2e%2f in the path parameter
• Web server access logs showing repeated requests to loader.php with varying path values targeting system files like /etc/passwd, /etc/shadow, or application configuration files
• Unexpected outbound traffic from the Mailinspector host following suspicious loader.php requests, suggesting credential reuse by an attacker

Detection Strategies

• Deploy web application firewall rules that block path traversal patterns in query strings and request bodies targeting loader.php
• Inspect HTTP request logs for traversal sequences and absolute paths submitted to the path parameter
• Correlate access to loader.php with the source IP reputation and the absence of an authenticated session cookie

Monitoring Recommendations

• Forward Mailinspector web server logs to a centralized SIEM and alert on anomalous request patterns to /public/loader.php
• Monitor file integrity and access timestamps on sensitive configuration files that the web server account can read
• Track outbound connections from the Mailinspector host to detect post-exploitation activity using leaked credentials

How to Mitigate CVE-2024-34470

Immediate Actions Required

• Upgrade HSC Mailinspector to a version later than 5.2.18 once a fixed release is available from HSC Brazil
• Restrict network access to the Mailinspector web interface using firewall rules or a reverse proxy that enforces authentication
• Audit the server for evidence of prior exploitation, including unauthorized access to configuration files and credential stores

Patch Information

No vendor advisory or patch reference is listed in the NVD record at the time of writing. Administrators should consult HSC Brazil directly for an official fixed version and apply it as soon as it is released. Until a patch is available, compensating controls must be enforced at the network and web server layers.

Workarounds

• Block external access to /public/loader.php at the reverse proxy or WAF until a vendor patch is applied
• Add WAF signatures that reject requests containing .., %2e%2e, or absolute path prefixes in the path parameter
• Run the Mailinspector web server process under a low-privilege account that cannot read sensitive system files
• Rotate any credentials, API keys, or certificates stored on the Mailinspector host that may have been exposed

# Example nginx rule to block path traversal attempts against loader.php
location /public/loader.php {
    if ($args ~* "(\.\./|%2e%2e|/etc/|/proc/)") {
        return 403;
    }
}