CVE-2017-3824 in IOS XE
Summary
by MITRE
A vulnerability in the handling of list headers in Cisco cBR Series Converged Broadband Routers could allow an unauthenticated, remote attacker to cause the device to reload, resulting in a denial of service (DoS) condition. Cisco cBR-8 Converged Broadband Routers running vulnerable versions of Cisco IOS XE are affected. More Information: CSCux40637. Known Affected Releases: 15.5(3)S 15.6(1)S. Known Fixed Releases: 15.5(3)S2 15.6(1)S1 15.6(2)S 15.6(2)SP 16.4(1).
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Analysis
by VulDB Data Team • 02/06/2020
The vulnerability identified as CVE-2017-3824 resides within the Cisco cBR Series Converged Broadband Routers, specifically affecting the handling of list headers in the Cisco IOS XE operating system. This flaw represents a critical denial of service vulnerability that can be exploited by unauthenticated remote attackers without requiring any special privileges or credentials. The affected devices include the cBR-8 Converged Broadband Routers running vulnerable software versions, making this a significant concern for network infrastructure security. The vulnerability stems from improper validation and processing of list header data structures within the router's software stack, creating a condition where malformed input can trigger unexpected behavior.
The technical nature of this vulnerability aligns with CWE-121, which describes heap-based buffer overflow conditions, and potentially CWE-122, which covers buffer overflow vulnerabilities. The flaw manifests when the router processes list headers containing malformed or specially crafted data, causing the system to enter an unstable state that ultimately results in a complete device reload. This behavior demonstrates characteristics consistent with the ATT&CK technique T1499.004, which involves network disruption through denial of service attacks. The vulnerability is particularly concerning because it operates at the protocol processing level, where the router's core software components handle incoming network traffic and data structures.
The operational impact of CVE-2017-3824 extends beyond simple service interruption, as the device reload process can disrupt critical network services and potentially cause cascading failures in connected systems. Network administrators may experience extended downtime while devices restart and re-establish network connections, leading to significant business disruption. The vulnerability affects multiple software releases including 15.5(3)S and 15.6(1)S, with the affected versions spanning across different major release branches. This widespread impact across multiple software versions indicates the fundamental nature of the flaw within the codebase, suggesting that the issue may be present in various configurations and deployment scenarios.
Organizations affected by this vulnerability should prioritize immediate implementation of the vendor-provided patches and updates, specifically targeting the fixed releases 15.5(3)S2, 15.6(1)S1, 15.6(2)S, 15.6(2)SP, and 16.4(1). The mitigation strategy should include comprehensive network monitoring to detect potential exploitation attempts and implementation of network segmentation to limit the attack surface. Security teams should also consider implementing intrusion detection systems that can identify malformed list header traffic patterns and establish baseline network behavior to quickly identify when devices begin exhibiting abnormal reloading patterns. The vulnerability's classification as a remote, unauthenticated attack vector means that organizations cannot rely on traditional network perimeter defenses alone to protect against exploitation, requiring a more comprehensive security approach that includes device hardening and continuous monitoring protocols.