Out-of-Bounds Read in libmodulemd YAML Serialization

Executive Summary

This vulnerability is an out-of-bounds read flaw in libmodulemd. When processing module stream v2 rpm-map data, an inner loop incorrectly uses the count of digest algorithms instead of the number of checksums. Crafted modulemd v2 metadata with multiple digest types can trigger this, causing a crash during YAML serialization and leading to a denial of service.

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Detection Guidance

Detecting this vulnerability requires checking for libmodulemd versions and parsing crafted modulemd v2 metadata. Inspect installed packages with 'rpm -qa | grep libmodulemd' or 'dnf list installed libmodulemd'. Monitor logs for crashes during YAML serialization of modulemd v2 documents. Use 'journalctl -u <service>' to check for application crashes after processing module metadata.

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Impact Analysis

The impact is a denial of service due to crashes when parsing and serializing malicious modulemd v2 metadata. It does not directly expose confidentiality or integrity risks but can disrupt services relying on libmodulemd for module stream processing.

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Compliance Impact

This vulnerability causes a denial of service via an out-of-bounds read during YAML serialization, which may lead to system crashes. It does not directly impact data confidentiality or integrity, so it likely has minimal direct effect on compliance with standards like GDPR or HIPAA that focus on data protection and availability.

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Mitigation Strategies

Avoid processing untrusted modulemd v2 documents containing artifacts.rpm-map with multiple digest algorithms. Strip rpm-map content with multiple digest entries before serialization. Temporarily disable modulemd v2 parsing if possible. Monitor vendor updates for libmodulemd fixes and apply them once available.

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