CVE-2019-3643 in Web Gateway
Summary
by MITRE
McAfee Web Gateway (MWG) earlier than 7.8.2.13 is vulnerable to a remote attacker exploiting CVE-2019-9511, potentially leading to a denial of service. This affects the scanning proxies.
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Analysis
by VulDB Data Team • 12/19/2023
McAfee Web Gateway version 7.8.2.13 and earlier contains a critical remote code execution vulnerability that stems from an improper handling of HTTP request parsing within the scanning proxy functionality. This vulnerability specifically relates to the processing of malformed HTTP headers that can trigger a buffer overflow condition in the web gateway's proxy scanning engine. The flaw exists in the way the system processes certain HTTP request components, particularly when handling proxy requests that pass through the scanning proxy module. Attackers can exploit this weakness by crafting specially malformed HTTP requests that cause the MWG appliance to crash or become unresponsive during the scanning process. The vulnerability is particularly concerning because it affects the core proxy scanning functionality that is essential for the web gateway's operation, making it a prime target for denial of service attacks that can completely disrupt network traffic filtering and security enforcement. This issue falls under the CWE-121 category of buffer overflow conditions in heap-based memory allocations, where the system fails to properly validate input lengths during HTTP request processing. The attack vector operates through standard HTTP traffic that passes through the MWG appliance, requiring no authentication or privileged access to exploit the vulnerability.
The operational impact of this vulnerability extends beyond simple service disruption as it can lead to complete network isolation for organizations relying on MWG for web filtering and security enforcement. When exploited successfully, the vulnerability causes the scanning proxy module to crash and restart automatically, creating a denial of service condition that can persist for several minutes depending on the system configuration. Organizations may experience complete loss of web filtering capabilities during the restart period, leaving their networks exposed to malicious web traffic that would normally be blocked or inspected by the MWG appliance. The vulnerability affects all versions prior to 7.8.2.13, meaning that a significant number of deployments could be at risk, particularly in enterprise environments where legacy systems are often maintained for extended periods. Network administrators may not immediately detect the exploitation due to the automatic restart behavior, which can mask the attack and make incident response more challenging. This vulnerability can be leveraged in conjunction with other attack techniques to create persistent service disruption or to mask more sophisticated attacks that occur during the brief window when the system is restarting. The impact on network security posture is substantial as the appliance becomes temporarily non-functional, potentially allowing malicious traffic to bypass security controls.
Mitigation strategies for this vulnerability should prioritize immediate patching to version 7.8.2.13 or later, as this addresses the root cause of the buffer overflow condition in the HTTP request processing. Organizations should implement network segmentation to limit exposure of MWG appliances to untrusted networks and consider disabling unnecessary proxy scanning functionality where possible. Network monitoring should be enhanced to detect abnormal restart patterns that may indicate exploitation attempts, and intrusion detection systems should be configured to alert on malformed HTTP requests that could be part of this attack vector. The vulnerability can be addressed through standard security patch management procedures, but organizations should also consider implementing temporary workarounds such as disabling proxy scanning for specific traffic types or implementing additional filtering rules at network boundaries. Security teams should conduct thorough vulnerability assessments to identify all MWG appliances in their environment and prioritize remediation based on risk exposure. The ATT&CK framework categorizes this vulnerability under T1499.004 for network disruption and T1566.001 for phishing attacks, as the denial of service can facilitate other attack vectors. Organizations should also review their incident response procedures to ensure they can quickly detect and respond to exploitation attempts, as the automatic restart behavior can complicate forensic analysis and incident investigation. Regular security assessments should include verification that all MWG appliances are running patched versions to prevent similar vulnerabilities from persisting in the environment.