CVE-2019-1884 in AsyncOS
Summary
by MITRE
A vulnerability in the web proxy functionality of Cisco AsyncOS Software for Cisco Web Security Appliance (WSA) could allow an authenticated, remote attacker to cause a denial of service (DoS) condition on an affected device. The vulnerability is due to insufficient input validation mechanisms for certain fields in HTTP/HTTPS requests sent through an affected device. A successful attacker could exploit this vulnerability by sending a malicious HTTP/HTTPS request through an affected device. An exploit could allow the attacker to force the device to stop processing traffic, resulting in a DoS condition.
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Analysis
by VulDB Data Team • 10/17/2023
The vulnerability identified as CVE-2019-1884 resides within the web proxy functionality of Cisco AsyncOS Software running on Cisco Web Security Appliances, representing a critical security weakness that undermines the availability of protected network services. This flaw specifically targets the input validation mechanisms that govern HTTP/HTTPS request processing through the web proxy component, creating a pathway for authenticated remote attackers to disrupt normal operational procedures. The vulnerability manifests when the system fails to adequately validate certain fields within incoming HTTP/HTTPS requests, allowing malformed or maliciously crafted data to bypass normal processing controls and potentially destabilize the entire appliance.
The technical exploitation of this vulnerability requires an authenticated attacker who can establish a connection to the affected WSA device and subsequently craft specific HTTP/HTTPS requests designed to trigger the input validation failure. This attack vector operates under the principle that insufficient sanitization of user-supplied data can lead to system instability, with the malicious requests containing specially formatted fields that cause the proxy processing engine to malfunction. The flaw falls under the category of inadequate input validation, which is classified as CWE-20 by the Common Weakness Enumeration taxonomy, specifically representing a weakness where input validation is not properly implemented or enforced. The vulnerability can be leveraged through the standard web proxy interface, making it accessible to attackers who have already established authentication credentials, whether through legitimate administrative access or compromised accounts.
The operational impact of CVE-2019-1884 extends beyond simple service disruption, as it represents a significant threat to network availability and business continuity for organizations relying on Cisco WSA appliances for web security filtering. When successfully exploited, the vulnerability forces the affected device to cease processing incoming traffic, effectively creating a denial of service condition that can block legitimate user access to web resources. This disruption can cascade through network operations, particularly in environments where the WSA serves as a primary gateway for internet access, potentially affecting thousands of users and applications. The attack requires minimal technical sophistication beyond establishing authentication access, making it particularly dangerous as it can be exploited by attackers with limited advanced capabilities. Organizations may experience extended downtime while system administrators investigate and remediate the issue, potentially disrupting critical business operations and requiring emergency response procedures.
Mitigation strategies for CVE-2019-1884 should focus on both immediate patching and operational security enhancements to reduce the attack surface. Cisco has released software updates addressing this vulnerability through the publication of security advisory Cisco Security Advisory 2019-2333, which provides the necessary firmware patches to resolve the input validation deficiencies. Organizations should prioritize immediate deployment of these patches across all affected WSA appliances to eliminate the vulnerability. Additionally, implementing network segmentation and access controls can help limit the potential impact of authenticated attacks, while monitoring systems should be configured to detect unusual traffic patterns or authentication attempts that might indicate exploitation attempts. The vulnerability demonstrates the importance of maintaining up-to-date security controls and proper input validation mechanisms, as outlined in the ATT&CK framework under the technique of privilege escalation and defense evasion. Regular security assessments and vulnerability scanning should be implemented to identify similar weaknesses in other network security components, ensuring comprehensive protection against both current and emerging threats in the cybersecurity landscape.