CVE-2017-3790 in Expressway
Summary
by MITRE
A vulnerability in the received packet parser of Cisco Expressway Series and Cisco TelePresence Video Communication Server (VCS) software could allow an unauthenticated, remote attacker to cause a reload of the affected system, resulting in a denial of service (DoS) condition. The vulnerability is due to insufficient size validation of user-supplied data. An attacker could exploit this vulnerability by sending crafted H.224 data in Real-Time Transport Protocol (RTP) packets in an H.323 call. An exploit could allow the attacker to overflow a buffer in a cache that belongs to the received packet parser, which will result in a crash of the application, resulting in a DoS condition. All versions of Cisco Expressway Series Software and Cisco TelePresence VCS Software prior to version X8.8.2 are vulnerable. Cisco has released software updates that address this vulnerability. There are no workarounds that address this vulnerability. Cisco Bug IDs: CSCus99263.
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Analysis
by VulDB Data Team • 11/04/2022
The vulnerability described in CVE-2017-3790 represents a critical buffer overflow condition affecting Cisco Expressway Series and Cisco TelePresence Video Communication Server software implementations. This weakness resides within the packet parser component responsible for processing incoming H.224 data within RTP packets during H.323 call signaling operations. The flaw manifests as inadequate input validation mechanisms that fail to properly enforce size constraints on user-supplied data streams, creating an exploitable condition that can be leveraged by remote attackers without authentication requirements. The vulnerability specifically impacts systems running software versions prior to X8.8.2, making it particularly concerning for organizations with legacy deployments that have not received the necessary security patches.
The technical exploitation of this vulnerability occurs through carefully crafted H.224 data payloads embedded within RTP packets that are part of standard H.323 call establishment procedures. When the affected software processes these malformed packets, the insufficient size validation allows an attacker to overflow a buffer within the received packet parser cache structure. This buffer overflow condition directly leads to application instability and subsequent system crash, ultimately resulting in a denial of service state where the targeted system becomes unavailable for legitimate communication operations. The vulnerability's classification aligns with CWE-121, which describes heap-based buffer overflow conditions, and represents a classic example of improper input validation leading to memory corruption issues. The attack vector operates entirely over network protocols without requiring any privileged access or authentication credentials, making it particularly dangerous for operational technology environments.
From an operational impact perspective, this vulnerability poses significant risk to organizations relying on Cisco VCS and Expressway systems for critical video communication services. The denial of service condition can disrupt business continuity by rendering video conferencing infrastructure unavailable, potentially affecting hundreds or thousands of users depending on the scale of deployment. The vulnerability's remote nature means that attackers can exploit it from outside the organization's network perimeter, eliminating the need for physical access or insider knowledge. The lack of available workarounds compounds the risk, as organizations cannot implement temporary mitigations while awaiting official patches. This situation creates a window of exposure where systems remain vulnerable until the security update is deployed, potentially allowing attackers to maintain persistent disruption or use the DoS condition as a precursor to more sophisticated attacks. The vulnerability also demonstrates the importance of maintaining current software versions and implementing robust patch management processes for critical communication infrastructure.
Organizations affected by this vulnerability should immediately prioritize the deployment of Cisco's security update addressing this issue, as no alternative mitigations exist. The recommended approach involves applying the official software patches released by Cisco to bring affected systems to version X8.8.2 or later, which contain the necessary fixes to validate packet sizes and prevent buffer overflow conditions. Security teams should conduct comprehensive vulnerability assessments to identify all impacted systems within their network infrastructure and establish monitoring procedures to detect potential exploitation attempts. The remediation process should include thorough testing of patches in non-production environments before deployment to ensure compatibility with existing network configurations and communication workflows. Additionally, organizations should implement network segmentation and access controls to limit exposure of critical VCS systems, while maintaining continuous monitoring for anomalous packet traffic patterns that might indicate attempted exploitation of this vulnerability. This vulnerability serves as a reminder of the critical importance of timely security updates in maintaining the integrity and availability of communication infrastructure, particularly in environments where video conferencing systems form the backbone of business operations and collaboration.