CVE-2015-4273 in ASR 5000
Summary
by MITRE
The Packet Data Network Gateway (aka PGW) component on Cisco ASR 5000 devices with software 15.0(912), 15.0(935), and 15.0(938) allows remote attackers to cause a denial of service (Session Manager outage) via malformed fields in an IP packet, aka Bug ID CSCut38476.
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Analysis
by VulDB Data Team • 06/01/2022
The Cisco ASR 5000 series devices operate as Packet Data Network Gateways within mobile network infrastructures, serving as critical components that manage session establishment and data routing for 3G and 4G cellular networks. These devices function as the interface between mobile networks and external packet data networks, handling session management and traffic control for millions of concurrent users. The vulnerability resides within the Session Manager component of the PGW functionality, which is responsible for maintaining session state information and managing the lifecycle of user data sessions. When these devices process malformed IP packet fields, the Session Manager component becomes unstable and experiences a complete outage, effectively disrupting all user services and creating a significant service disruption for network operators.
This vulnerability represents a classic buffer overflow and input validation failure that manifests through malformed packet processing within the network infrastructure. The flaw occurs when the PGW component receives IP packets containing malformed fields that exceed expected parameter boundaries or contain invalid data structures. The specific nature of the vulnerability involves improper handling of packet header fields, particularly those related to tunneling protocols and session identifiers used in the GPRS Tunneling Protocol (GTP). According to CWE classification, this vulnerability maps to CWE-121, which describes heap-based buffer overflow conditions, and CWE-125, which covers out-of-bounds read vulnerabilities. The attack vector is particularly dangerous because it requires only a single malformed packet to trigger the denial of service condition, making it highly exploitable from remote network locations.
The operational impact of CVE-2015-4273 extends far beyond simple service disruption, as it can affect entire network segments and potentially compromise the reliability of critical communication services. When the Session Manager component fails, all active user sessions are terminated, requiring complete re-establishment of network connectivity for affected users. This creates cascading effects throughout the mobile network infrastructure, as the failure impacts not only the immediate device but also dependent systems that rely on session state information. The vulnerability affects multiple software versions including 15.0(912), 15.0(935), and 15.0(938), indicating a widespread issue that would require coordinated patching across multiple network installations. Network operators face significant challenges in maintaining service availability when such core infrastructure components become unavailable, as the recovery process typically involves manual intervention and system restart procedures that can take hours to complete.
Mitigation strategies for this vulnerability should focus on both immediate defensive measures and long-term architectural improvements. Network operators should implement packet filtering rules at network boundaries to identify and drop malformed IP packets before they reach the vulnerable PGW components. The implementation of intrusion prevention systems with signature-based detection capabilities can help identify and block exploitation attempts. Additionally, network administrators should establish monitoring protocols to detect early signs of Session Manager instability and implement automated failover mechanisms to minimize service disruption. According to ATT&CK framework, this vulnerability aligns with techniques involving network denial of service attacks and system compromise through exploitation of infrastructure components. Cisco recommends applying the appropriate software patches as soon as they become available, while also implementing network segmentation strategies to limit the potential impact of similar vulnerabilities in other network components. Regular security assessments and vulnerability scanning should be conducted to identify similar weaknesses in network infrastructure components that could serve as attack vectors for future exploits.