Compliance Impact

The vulnerability allows unauthenticated attackers to read arbitrary files, including sensitive system files, if the servlet engine runs with elevated privileges. This unauthorized access to sensitive data could lead to violations of data protection standards and regulations such as GDPR and HIPAA, which require strict controls to prevent unauthorized access to personal and sensitive information.

Because attackers can exploit this path traversal flaw to access files outside the intended webroot, any sensitive data stored on the server could be exposed, potentially resulting in non-compliance with regulations that mandate confidentiality and integrity of protected data.

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Executive Summary

CVE-2026-56122 is a path traversal vulnerability in the Winstone Servlet Engine version 0.9.10 and earlier. It allows unauthenticated attackers to read arbitrary files on the server by sending specially crafted HTTP GET requests containing dot-dot-slash sequences. These sequences are not properly sanitized when serving static files from the configured webroot, enabling attackers to traverse outside the webroot directory.

This means an attacker can access any file that the servlet engine process has permission to read, including sensitive system files if the service runs with elevated privileges.

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Impact Analysis

This vulnerability can have serious impacts because it allows attackers to read arbitrary files on the server without authentication.

• Attackers can access sensitive system files such as /etc/passwd or /etc/shadow, potentially exposing user credentials or other critical information.
• If the servlet engine runs with elevated privileges, the attacker’s ability to read sensitive files increases, which can lead to further exploitation or system compromise.
• The unauthorized disclosure of sensitive information can lead to data breaches, loss of confidentiality, and damage to system integrity.

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Detection Guidance

This vulnerability can be detected by monitoring HTTP GET requests for suspicious path traversal patterns, specifically requests containing dot-dot-slash sequences (../) that attempt to access files outside the webroot directory.

A practical detection method is to analyze web server logs or capture network traffic for HTTP requests with traversal sequences.

• Use tools like tcpdump or Wireshark to capture HTTP traffic and filter for requests containing '../' sequences.
• Example tcpdump command: tcpdump -A -s 0 'tcp port 80 and (((ip[2:2] - ((ip[0]&0xf)<<2)) - ((tcp[12]&0xf0)>>2)) != 0)' | grep '../'
• Search web server access logs for suspicious requests, e.g., using grep: grep '\.\./' /path/to/access.log

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Mitigation Strategies

Immediate mitigation steps include restricting access to the vulnerable Winstone Servlet Engine and preventing exploitation of the path traversal flaw.

• Block or filter HTTP requests containing dot-dot-slash sequences (../) at the web server or network firewall level.
• Run the servlet engine with the least privileges possible to limit the impact of any file access.
• If possible, disable serving static files from the webroot or restrict the webroot directory permissions to prevent unauthorized file reads.
• Monitor logs for exploitation attempts and respond accordingly.

Since the software is unsupported and no patches are available, consider upgrading to a different servlet engine or applying custom patches to sanitize path traversal sequences.

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