CVE-2015-6293 in Web Security Appliance
Summary
by MITRE
Cisco AsyncOS 8.x before 8.0.8-113, 8.1.x and 8.5.x before 8.5.3-051, 8.6.x and 8.7.x before 8.7.0-171-LD, and 8.8.x before 8.8.0-085 on Web Security Appliance (WSA) devices allows remote attackers to cause a denial of service (memory consumption) via multiple file-range requests, aka Bug ID CSCur39155.
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Analysis
by VulDB Data Team • 06/26/2022
Cisco AsyncOS versions prior to specific patch releases contain a vulnerability that enables remote attackers to consume excessive memory resources through crafted file-range requests on Web Security Appliance devices. This vulnerability specifically affects WSA appliances running AsyncOS versions 8.0.x before 8.0.8-113, 8.1.x versions, 8.5.x before 8.5.3-051, 8.6.x and 8.7.x before 8.7.0-171-LD, and 8.8.x before 8.8.0-085. The flaw manifests when multiple file-range requests are processed in succession, leading to uncontrolled memory consumption that ultimately results in denial of service conditions.
The technical nature of this vulnerability stems from inadequate input validation and resource management within the AsyncOS file handling mechanisms. When multiple range requests are submitted to the web security appliance, the system fails to properly limit or track memory allocation for these operations, allowing attackers to exhaust available memory resources through repeated requests. This memory exhaustion occurs without proper bounds checking or resource limiting controls, making it particularly susceptible to exploitation by remote unauthenticated attackers who can simply send malformed requests to trigger the condition.
The operational impact of this vulnerability extends beyond simple service disruption to potentially compromise the overall security posture of organizations relying on Cisco WSA appliances for web security. A successful exploitation can render the appliance non-functional, blocking all web traffic and potentially exposing the network to additional threats during the downtime. The vulnerability affects the core functionality of the web security appliance, which is designed to filter and monitor web traffic, making it a critical target for attackers seeking to disrupt business operations or gain unauthorized access to network resources.
Organizations affected by this vulnerability should prioritize immediate patching of their Cisco WSA appliances to the latest available versions that contain the necessary fixes. The remediation process involves upgrading to AsyncOS versions 8.0.8-113 or later for 8.0.x releases, 8.5.3-051 or later for 8.5.x releases, 8.7.0-171-LD or later for 8.6.x and 8.7.x releases, and 8.8.0-085 or later for 8.8.x releases. Security administrators should also implement network monitoring to detect unusual traffic patterns that might indicate exploitation attempts and consider implementing rate limiting controls to prevent abuse of the affected functionality. This vulnerability aligns with CWE-400, which describes improper resource management, and maps to ATT&CK technique T1499.004 for network denial of service attacks, emphasizing the importance of proper resource allocation and input validation in security appliance design.