CVE-2017-8294 in YARA
Summary
by MITRE
libyara/re.c in the regex component in YARA 3.5.0 allows remote attackers to cause a denial of service (out-of-bounds read and application crash) via a crafted rule that is mishandled in the yr_re_exec function.
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Analysis
by VulDB Data Team • 12/02/2022
The vulnerability identified as CVE-2017-8294 resides within the YARA threat intelligence framework version 3.5.0, specifically within the libyara/re.c component that handles regular expression processing. This flaw represents a critical security issue that affects the core functionality of YARA's pattern matching capabilities, which are extensively used by security professionals for malware detection and threat hunting operations. The vulnerability manifests as an out-of-bounds read condition that occurs when the yr_re_exec function processes malformed regular expression rules, potentially leading to application instability and complete system denial of service.
The technical exploitation of this vulnerability occurs through the improper handling of crafted regular expression patterns within YARA rules. When an attacker submits a specially constructed rule that triggers the yr_re_exec function, the regex engine fails to properly validate input boundaries, resulting in memory access violations that cause the application to crash. This out-of-bounds read condition stems from inadequate bounds checking in the regular expression engine's execution logic, where memory locations beyond the allocated buffer are accessed without proper validation. The flaw is particularly dangerous because it can be triggered remotely through any mechanism that allows rule submission to the YARA engine, including network-based scanning tools or automated threat analysis platforms that utilize YARA for pattern matching.
The operational impact of CVE-2017-8294 extends beyond simple application crashes, as it fundamentally compromises the reliability of security tools that depend on YARA's pattern matching capabilities. Security operations centers that rely on YARA for malware detection, threat intelligence analysis, or automated scanning processes face significant risk of service disruption when encountering maliciously crafted rules. This vulnerability can be leveraged in a denial of service attack against security infrastructure, potentially causing widespread disruption in threat hunting operations, malware analysis workflows, and automated security monitoring systems. The impact is amplified because YARA is widely deployed across various security tools and platforms, making this vulnerability a potential vector for cascading service failures throughout security ecosystems.
Mitigation strategies for CVE-2017-8294 should prioritize immediate patching of affected YARA installations to version 3.6.0 or later, where the vulnerability has been addressed through improved input validation and bounds checking in the regular expression engine. Organizations should also implement defensive measures such as restricting rule submission privileges, implementing input sanitization for all YARA rule processing, and establishing monitoring for anomalous rule execution patterns that might indicate exploitation attempts. From a cybersecurity framework perspective, this vulnerability aligns with CWE-125, which describes out-of-bounds read conditions, and represents a clear example of how regex engine vulnerabilities can be exploited for denial of service attacks. The ATT&CK framework categorizes this as a technique for maintaining access through service stoppage, where adversaries can disrupt security operations by targeting core infrastructure components. Additionally, security teams should consider implementing sandboxing mechanisms for rule processing and establishing secure coding practices for regex engine implementations to prevent similar vulnerabilities from emerging in other security tools.