CVE-2016-3986 in Avast
Summary
by MITRE
Avast allows remote attackers to cause a denial of service (memory corruption) and possibly execute arbitrary code via a crafted PE file, related to authenticode parsing.
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Analysis
by VulDB Data Team • 02/09/2025
The vulnerability identified as CVE-2016-3986 resides within Avast's security software, specifically affecting its handling of Authenticode signatures within Portable Executable files. This flaw represents a critical security issue that demonstrates how legitimate security tools can themselves become attack vectors when processing malformed input. The vulnerability manifests during the parsing of PE files that contain crafted Authenticode signatures, which are used to verify the authenticity and integrity of Windows executables. When Avast encounters such malformed signatures, the software's parsing logic fails to properly validate the input structure, leading to memory corruption that can result in arbitrary code execution or complete system denial of service.
The technical implementation of this vulnerability stems from insufficient input validation within Avast's PE file analysis engine. The software's Authenticode parser does not adequately sanitize or verify the structure of signature data contained within PE files, allowing attackers to craft malicious files that exploit buffer overflows or other memory corruption issues during signature processing. This type of vulnerability aligns with CWE-121, which describes heap-based buffer overflow conditions, and CWE-125, which covers out-of-bounds read errors. The flaw operates at the intersection of code analysis and security verification, where the legitimate function of verifying software authenticity becomes a vector for exploitation. Attackers can leverage this vulnerability by preparing specially crafted PE files that contain malformed Authenticode signatures designed to trigger the memory corruption during Avast's scanning process.
The operational impact of CVE-2016-3986 extends beyond simple denial of service, as the vulnerability could potentially enable remote code execution on systems running affected Avast versions. This represents a significant concern for enterprise environments where Avast is deployed as a comprehensive security solution, as it could allow attackers to compromise systems without requiring direct access to the target machine. The vulnerability affects not only individual user systems but also enterprise security infrastructure that relies on Avast for malware detection and prevention. Organizations using Avast may experience complete service disruption when the vulnerability is exploited, leading to potential data loss, system compromise, or complete operational downtime. The attack surface is particularly concerning because PE files are ubiquitous in Windows environments, making this vulnerability highly exploitable across various network configurations and security postures.
Mitigation strategies for CVE-2016-3986 focus on immediate software updates and operational security measures. Organizations should prioritize applying the latest security patches from Avast that address the Authenticode parsing vulnerability, as the vendor released specific fixes for this issue. Network administrators should implement additional monitoring for suspicious PE file patterns and consider temporary disabling of Avast's PE file analysis features until patches are deployed. Security teams should also implement network segmentation and access controls to limit potential exploitation, while maintaining detailed logging of file analysis activities to detect anomalous behavior. The vulnerability's classification under the ATT&CK framework would place it within the T1059.007 technique category, which involves execution through scripting, and T1489, which covers denial of service attacks. Organizations should also consider implementing sandboxing mechanisms for suspicious file analysis to prevent the exploitation of such vulnerabilities in production environments. Regular security assessments and vulnerability scanning should include verification of Avast's configuration and ensure that all security features are properly updated and functioning to prevent exploitation of this and similar vulnerabilities.