Arbitrary Code Execution in SpeechBrain via Unsafe YAML Parsing

Executive Summary

This vulnerability in SpeechBrain before version 1.1.1 allows arbitrary code execution through a crafted CKPT.yaml checkpoint metadata file. The issue occurs because the software uses PyYAML's unsafe loader to parse these files during candidate enumeration. Attackers can embed malicious Python object construction tags like !!python/object/apply in the CKPT.yaml file. When the Checkpointer.recover_if_possible() function processes this file, it executes the embedded code, even if the malicious checkpoint is never selected for recovery.

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Detection Guidance

To detect this vulnerability, inspect any CKPT.yaml files in your SpeechBrain checkpoint directories for suspicious YAML tags like !!python/object/apply. Use commands such as 'find / -name CKPT.yaml -type f -exec grep -l "!!python/object" {} \;' to search for malicious patterns. Also check for unsafe YAML loader usage in code with 'grep -r "yaml.Loader" /path/to/speechbrain/'.

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Impact Analysis

If you use SpeechBrain versions before 1.1.1, an attacker could exploit this flaw to execute arbitrary code on your system. This could lead to unauthorized access, data theft, or system compromise. The vulnerability is triggered simply by placing a malicious CKPT.yaml file in the checkpoint path, making it a significant risk for users who rely on SpeechBrain for speech processing tasks.

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Compliance Impact

This vulnerability could lead to unauthorized code execution, potentially resulting in data breaches or unauthorized access to sensitive information. For organizations subject to GDPR or HIPAA, such incidents may violate compliance requirements, leading to legal penalties, reputational damage, and loss of customer trust. The high CVSS score indicates the severity of the risk.

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Mitigation Strategies

Immediately upgrade SpeechBrain to version 1.1.1 or later. Replace any unsafe YAML loader usage with yaml.SafeLoader in your codebase. Remove any CKPT.yaml files containing suspicious Python object construction tags like !!python/object/apply.

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