YARA Assertion Failure in Compiled Rule File Handling

Executive Summary

This vulnerability is a reachable assertion flaw in YARA 4.5.8 where crafted .yrc files with an invalid arena configuration (num_buffers=0) trigger an assertion failure in yr_arena_get_ptr(). This causes the application to crash with a SIGABRT when assertions are enabled, leading to a denial-of-service condition.

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Detection Guidance

To detect this vulnerability, monitor for crashes in YARA when processing .yrc files. Use the yara CLI with the -C flag on suspicious files to trigger the assertion failure if the file contains num_buffers=0. Check for SIGABRT signals or exit code 134 during YARA operations.

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Impact Analysis

An attacker can exploit this by providing a malicious .yrc file to crash YARA, causing a denial-of-service. The impact depends on how YARA is used: if integrated into security tools, it could disrupt scanning processes. Systems using assert-enabled YARA builds are more vulnerable than those with NDEBUG builds, which handle the error gracefully.

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Compliance Impact

This vulnerability primarily causes a denial-of-service condition by crashing YARA when processing crafted .yrc files, which could disrupt security scanning workflows. For compliance standards like GDPR or HIPAA that require continuous monitoring and data integrity, such disruptions might lead to gaps in threat detection or audit trails. However, the vulnerability does not directly expose or leak data, so its impact on compliance is indirect through service availability rather than data protection.

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Mitigation Strategies

Upgrade YARA to a patched version that includes the fix for arena buffer validation. Avoid using assert-enabled builds of YARA 4.5.8. Validate .yrc files before processing to ensure num_buffers is not zero. Implement file integrity checks to detect corrupted files.

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