Executive Summary

[{'type': 'paragraph', 'content': 'CVE-2026-32771 is a path traversal vulnerability in the CTFer.io Monitoring component, specifically in the sanitizeArchivePath function within the pkg/extract/extract.go file. The function is responsible for sanitizing file paths extracted from tar archives but fails to properly validate paths due to a missing trailing path separator in a prefix check. This flaw allows crafted archive entries with directory traversal sequences to bypass the check and write files outside the intended extraction directory.'}, {'type': 'paragraph', 'content': 'An attacker can exploit this by providing a malicious archive containing paths like "../extract-outputevil/pwned" that appear to be inside the target directory but actually escape it. This enables arbitrary file writes on the host system, such as overwriting shell configuration files, SSH keys, Kubernetes config files, or crontabs.'}, {'type': 'paragraph', 'content': 'The vulnerability is exacerbated by the default ReadWriteMany Persistent Volume Claim (PVC) access mode, which allows any pod in the cluster to inject malicious payloads. The issue was fixed in version 0.2.2 by improving the path sanitization check to include the trailing path separator, preventing directory traversal attacks during archive extraction.'}] [1, 3]

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Impact Analysis

This vulnerability allows attackers to perform arbitrary file writes on the host system running the vulnerable extractor. This can lead to several severe impacts:

• Overwriting shell configuration files (e.g., ~/.bashrc, ~/.zshrc) to achieve remote code execution when the user next logs in.
• Appending entries to ~/.ssh/authorized_keys to establish persistent SSH backdoor access.
• Modifying Kubernetes configuration files (~/.kube/config) to hijack cluster access.
• Inserting malicious crontab entries for persistent scheduled execution of malicious code.

Because the vulnerability can be exploited remotely without privileges or user interaction, and due to the shared PVC access mode, any pod in the cluster can inject malicious archives, amplifying the attack surface.

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Compliance Impact

I don't know

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Detection Guidance

[{'type': 'paragraph', 'content': 'Detection of this vulnerability involves identifying the presence of vulnerable versions of the CTFer.io Monitoring component prior to version 0.2.2, especially focusing on the use of the extractor functions that handle archive extraction without proper path sanitization.'}, {'type': 'paragraph', 'content': 'Since the vulnerability arises from improper path validation during archive extraction, you can detect exploitation attempts by monitoring for suspicious archive files containing directory traversal paths (e.g., filenames with sequences like "../") being extracted.'}, {'type': 'paragraph', 'content': 'Suggested commands to help detect potential exploitation or presence of malicious files include:'}, {'type': 'list_item', 'content': 'Searching for suspicious files outside expected extraction directories, for example: `find /path/to/extraction -type f -name "*..*"` or `find / -path "*/..*"` to locate files with traversal patterns.'}, {'type': 'list_item', 'content': 'Checking for recently modified or created files in sensitive locations such as shell config files (`~/.bashrc`, `~/.zshrc`), SSH authorized keys (`~/.ssh/authorized_keys`), kubeconfig files, or crontabs that could indicate exploitation.'}, {'type': 'list_item', 'content': 'Using audit or file integrity monitoring tools (e.g., auditd, Tripwire) to detect unexpected changes in critical files.'}, {'type': 'list_item', 'content': 'Reviewing logs for extraction operations or pod activities that write archives to shared ReadWriteMany PVCs, which could be abused to inject malicious payloads.'}] [2, 3]

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Mitigation Strategies

The primary mitigation step is to upgrade the CTFer.io Monitoring component to version 0.2.2 or later, where the vulnerability in the sanitizeArchivePath function has been fixed by properly validating archive extraction paths.

Additional immediate steps include:

• Restrict write access to the ReadWriteMany Persistent Volume Claim (PVC) used by the monitoring stack to trusted pods only, preventing arbitrary pods from injecting malicious archives.
• Audit and monitor archive extraction code and processes to ensure they include proper path sanitization checks that prevent directory traversal.
• Implement security controls such as file integrity monitoring and runtime security tools to detect and block unauthorized file writes.
• Review and harden shell configuration files, SSH keys, kubeconfig files, and crontabs to detect and remove any unauthorized modifications.

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