Gogs Git Diff Command Injection Vulnerability

Executive Summary

This vulnerability exists in Gogs, an open source self-hosted Git service, in versions prior to 0.14.0. An authorized user can manipulate the value passed to the git diff command. By bypassing the filtering of this value, the user can escape the intended target directory and write the output of the git diff comparison to any arbitrary file path.

This means that an intruder with authorized access can potentially write files to locations they should not have access to, which can lead to unauthorized modifications on the system.

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Impact Analysis

The vulnerability allows an authorized user to write files to arbitrary paths on the system by exploiting the git diff command. This can lead to unauthorized file modifications, potentially causing integrity issues or enabling further attacks.

The CVSS score of 8.5 (High) indicates a significant impact, including the possibility of high availability impact (A:H) and integrity loss (I:L). This could disrupt service availability or compromise the integrity of data.

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Mitigation Strategies

To mitigate this vulnerability, you should upgrade Gogs to version 0.14.0 or later, where the issue has been fixed.

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Compliance Impact

The provided information does not specify how this vulnerability directly affects compliance with common standards and regulations such as GDPR or HIPAA.

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Detection Guidance

This vulnerability can be detected by checking if your Gogs instance is running a vulnerable version (0.13.4 or earlier) and by monitoring for unusual or unauthorized usage of the git diff command with manipulated path parameters.

Specifically, detection involves looking for attempts to exploit the path traversal flaw by observing requests that manipulate the `treePath` parameter in the `_preview` method or git diff commands that use the `--output` flag to write to arbitrary paths.

Suggested commands to help detect exploitation attempts include:

• Check the Gogs version to confirm if it is vulnerable: `gogs --version` or check the installed package version.
• Monitor git diff commands executed on the server for suspicious `--output` usage, for example, by reviewing shell history or process logs: `ps aux | grep 'git diff'`.
• Inspect web server or application logs for requests containing unusual `treePath` parameters or attempts to access paths outside the repository directory.
• Use file integrity monitoring tools to detect unexpected changes to critical files like `gogs.db` or `app.ini`.

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