CVE-2016-1405 in Web Security Appliance
Summary
by MITRE
libclamav in ClamAV (aka Clam AntiVirus), as used in Advanced Malware Protection (AMP) on Cisco Email Security Appliance (ESA) devices before 9.7.0-125 and Web Security Appliance (WSA) devices before 9.0.1-135 and 9.1.x before 9.1.1-041, allows remote attackers to cause a denial of service (AMP process restart) via a crafted document, aka Bug IDs CSCuv78533 and CSCuw60503.
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Analysis
by VulDB Data Team • 08/22/2022
The vulnerability identified as CVE-2016-1405 represents a critical denial of service weakness within the ClamAV antivirus engine implementation on Cisco security appliances. This flaw affects Advanced Malware Protection (AMP) functionality deployed on Cisco Email Security Appliance (ESA) and Web Security Appliance (WSA) devices, specifically targeting versions prior to 9.7.0-125 for ESA and various versions before 9.0.1-135 and 9.1.1-041 for WSA. The vulnerability stems from insufficient input validation within the libclamav library component that processes email attachments and web content for malware detection purposes. Attackers can exploit this weakness by crafting specially formatted documents that trigger unexpected behavior in the ClamAV processing pipeline, leading to complete process restarts and service disruption.
The technical nature of this vulnerability aligns with CWE-129, which describes improper validation of input boundaries, and demonstrates how insufficient validation can lead to process termination. The flaw operates through the document parsing mechanisms within ClamAV's engine where crafted input data causes memory corruption or buffer overflows that result in the AMP process crashing and automatically restarting. This type of vulnerability is particularly dangerous in security appliance environments where continuous protection is essential for network security operations. The attack vector involves sending malicious email messages or accessing compromised web content that contains the specially crafted document, which then passes through the ClamAV processing chain and triggers the exploitable condition.
The operational impact of CVE-2016-1405 extends beyond simple service disruption to represent a significant threat to network security continuity and availability. When the AMP process restarts due to this vulnerability, it creates gaps in malware detection coverage that attackers can exploit to bypass security controls. The restart process also generates significant logging activity and can overwhelm network monitoring systems with alert spam. Organizations using affected Cisco appliances face potential exposure to advanced persistent threats that could leverage the service disruption to deliver malware payloads during the brief window when protection is temporarily disabled. This vulnerability particularly impacts email security operations where the ESA appliance processes thousands of messages per hour, making the service disruption potentially catastrophic for email security operations.
Mitigation strategies for CVE-2016-1405 should prioritize immediate software updates to the affected Cisco appliance versions, specifically upgrading to the patched releases mentioned in the vulnerability description. Network administrators should implement additional monitoring for unusual process restart patterns in the AMP service and establish automated alerting for such events. The vulnerability also highlights the importance of input sanitization and validation within security appliances, aligning with ATT&CK technique T1499.004 for network denial of service. Organizations should consider implementing network segmentation to limit the impact of such vulnerabilities and establish redundant security controls to maintain protection during potential service disruptions. Regular security assessments and vulnerability scanning should be conducted to identify similar weaknesses in other security components, as this vulnerability demonstrates how seemingly minor input validation issues can create significant operational risks in enterprise security infrastructure.