Comprehensive Security Analysis: Vulnerabilities in PyYAML Explored

Original Post: Fully loaded: testing vulnerable PyYAML versions

The content summarizes the vulnerabilities of the PyYAML API across various versions:

1. The yaml.Loader class is unsafe in all released versions of PyYAML.
2. Methods like yaml.load(...), yaml.full_load(...) and their _all variants have become safe from known exploits after version 5.4.
3. yaml.safe_load(...) is safe in all versions.

The article discusses a GitHub user’s pull request to update a Semgrep rule for detecting unsafe yaml.full_load(...) usage and the subsequent analysis of how PyYAML’s API has evolved.

Key points:

• yaml.load(...) has been known to pose deserialization vulnerabilities.
• PyYAML patched certain vulnerabilities in versions 5.1 and 5.4.
• Testing methodologies and payloads were used to ascertain the safety of different APIs across versions.
• Recommendations include using safe_load for better security or updating to safer versions if using older PyYAML packages.
• The Semgrep rule update now alerts on APIs vulnerable after version 5.4 to improve security checks.

Additionally, the author encourages a hands-on approach to validate software safety and invites readers to join a community Slack for further engagement.

Go here to read the Original Post