CVE-2024-40445: Ctan Mimetex Path Traversal Vulnerability

CVE-2024-40445 Overview

CVE-2024-40445 is a directory traversal vulnerability [CWE-77] in forkosh MimeTeX before version 1.77. MimeTeX is a CGI program that renders LaTeX mathematical expressions as GIF images, often embedded in web applications. The flaw allows unauthenticated network attackers to read or append arbitrary files on Windows hosts by supplying crafted input paths. Exploitation requires no privileges and no user interaction. The issue is specific to MimeTeX deployments on Windows systems, where path handling fails to properly restrict access outside the intended directory.

Critical Impact

Unauthenticated remote attackers can read or append arbitrary files on Windows servers running MimeTeX before 1.77, leading to information disclosure and potential file tampering.

Affected Products

• forkosh MimeTeX versions prior to 1.77
• CTAN MimeTeX (cpe:2.3:a:ctan:mimetex:*)
• MimeTeX CGI deployments running on Windows hosts

Discovery Timeline

• 2025-04-22 - CVE-2024-40445 published to the National Vulnerability Database
• 2025-06-23 - Last updated in NVD database

Technical Details for CVE-2024-40445

Vulnerability Analysis

MimeTeX accepts LaTeX expressions via HTTP request parameters and renders them as images. The vulnerable code path handles file references embedded in the input expression. On Windows, the application fails to normalize and validate paths before opening files referenced by the user-supplied expression. An attacker can include traversal sequences such as ..\ or absolute Windows paths in the request, causing MimeTeX to read or append files outside the intended working directory. The flaw is exposed through the standard CGI interface, so any web-facing instance is reachable over the network. Public exploit code is available in a GitHub repository, demonstrating both arbitrary file read and arbitrary file append on Windows targets.

Root Cause

The root cause is missing input validation on file-path arguments parsed from LaTeX expressions in mimetex.c. The function responsible for opening referenced files does not strip directory traversal sequences or enforce a chroot-like base directory. Windows path semantics, including backslash separators and drive letters, are not handled defensively. See the MimeTeX source reference for the affected code region.

Attack Vector

The attack vector is network-based through the MimeTeX CGI endpoint. An attacker crafts an HTTP request whose LaTeX expression embeds a traversal payload pointing at a sensitive file, such as a configuration file or application log. MimeTeX opens the target file during rendering and reflects its contents or appends attacker-controlled data. No authentication is required. A public proof-of-concept is documented at the CVE-2024-40445 exploit repository.

No verified code examples are available. Refer to the MimeTeX source reference and the public proof-of-concept for technical details.

Detection Methods for CVE-2024-40445

Indicators of Compromise

• HTTP requests to MimeTeX CGI endpoints containing ..\, ../, or Windows drive letters such as C:\ inside the expression parameter.
• Web server access logs showing GET or POST requests with unusually long or path-like LaTeX inputs targeting mimetex.cgi.
• Unexpected read or append activity on sensitive Windows files originating from the MimeTeX process.

Detection Strategies

• Inspect web access logs for query strings to mimetex.cgi containing traversal sequences or absolute paths.
• Deploy a web application firewall rule that blocks traversal patterns in any MimeTeX request parameter.
• Correlate process file-access telemetry on Windows hosts with parent process mimetex.exe to flag access outside its working directory.

Monitoring Recommendations

• Enable file integrity monitoring on directories adjacent to and above the MimeTeX install path on Windows servers.
• Alert on outbound HTTP responses from MimeTeX that contain content matching sensitive file signatures, such as Windows configuration or credential files.
• Track the MimeTeX binary version in asset inventory and flag any instance running below 1.77.

How to Mitigate CVE-2024-40445

Immediate Actions Required

• Upgrade MimeTeX to version 1.77 or later on all Windows hosts running the CGI.
• Restrict network exposure of the MimeTeX endpoint to trusted internal users until the patch is applied.
• Audit Windows file system access logs for evidence of prior exploitation against MimeTeX-hosting servers.

Patch Information

Upgrade to forkosh MimeTeX 1.77 or later, which addresses the directory traversal handling on Windows. Refer to the vendor advisory and proof-of-concept repository for version details and remediation context.

Workarounds

• Place MimeTeX behind a reverse proxy or WAF that rejects requests containing ..\, ../, or absolute path indicators in any parameter.
• Run the MimeTeX process under a low-privilege Windows service account with read-only access scoped to its required directories.
• Disable MimeTeX entirely on Windows hosts where it is not actively required for LaTeX rendering.

# Example WAF rule (ModSecurity) to block traversal payloads to mimetex.cgi
SecRule REQUEST_URI "@contains mimetex.cgi" \
    "chain,deny,status:403,id:1004045,msg:'CVE-2024-40445 traversal attempt'"
    SecRule ARGS "@rx (\.\.[\\/]|[A-Za-z]:\\)" "t:none,t:urlDecode"