Executive Summary

This vulnerability is a path traversal flaw found in the hs-web hsweb-framework up to version 5.0.1, specifically in the file upload component. It occurs due to improper handling of the filename argument in the file upload function, allowing attackers to manipulate the file path and traverse directories outside the intended upload location.

Attackers can exploit this remotely by crafting filenames that include sequences like "../" or other encoded variants to escape the designated upload directory and write files to arbitrary locations on the server.

The vulnerability was addressed by enhancing filename validation, normalizing filenames to prevent Unicode-based attacks, replacing backslashes with forward slashes, restricting allowed characters, and using Java NIO Path operations to ensure safe path resolution and prevent traversal sequences.

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Impact Analysis

This vulnerability can have serious impacts because it allows an attacker to overwrite critical files on the server by escaping the intended upload directory.

• Overwriting important server files such as JAR files, which can lead to classpath poisoning and execution of arbitrary code.
• Modifying sensitive configuration files like SSH configurations or scheduled tasks, potentially leading to unauthorized access or persistence.

Overall, exploitation can lead to remote code execution, server compromise, data loss, or service disruption.

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Detection Guidance

This vulnerability involves path traversal through manipulation of the filename argument in the file upload functionality of hs-web hsweb-framework. Detection can focus on monitoring file upload requests for suspicious patterns such as directory traversal sequences (e.g., "../"), URL-encoded traversal sequences, or unusual Unicode encodings.

You can detect attempts by inspecting web server logs or network traffic for file upload requests containing these suspicious patterns.

• Use command-line tools like grep to search logs for traversal patterns, for example: grep -E '\.\./|%2e%2e|%252e%252e' /path/to/access.log
• Use network monitoring tools (e.g., tcpdump or Wireshark) to capture HTTP POST requests to the file upload endpoint and filter for suspicious filename parameters.
• If you have access to the application logs or can enable debug logging, look for exceptions or errors related to invalid file paths or path normalization failures.

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Mitigation Strategies

The primary mitigation is to apply the official patch identified by commit 8009845b577d8a2c4bbf4fdd8e8913799a714be6, which fixes the path traversal vulnerability by enhancing filename validation and normalization.

Until the patch can be applied, immediate steps include sanitizing and validating all file upload paths to remove or reject directory traversal sequences such as "../" and ensuring that file paths are normalized and constrained within the intended upload directory.

Additionally, restrict file upload permissions and monitor file system changes to detect unauthorized file writes.

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Compliance Impact

The vulnerability allows path traversal attacks through file upload functionality, enabling attackers to overwrite critical server files and potentially execute arbitrary code or modify sensitive configurations.

Such unauthorized access and manipulation of server files could lead to breaches of data confidentiality, integrity, and availability, which are core principles in standards like GDPR and HIPAA.

If exploited, this vulnerability could result in unauthorized access to personal or protected health information, thereby violating compliance requirements for data protection and security controls mandated by these regulations.

Therefore, failure to patch this vulnerability may expose organizations to regulatory non-compliance risks, potential data breaches, and associated legal and financial consequences.

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