CVE-2013-5503 in IOS XR
Summary
by MITRE
The UDP process in Cisco IOS XR 4.3.1 does not free packet memory upon detecting full packet queues, which allows remote attackers to cause a denial of service (memory consumption) via UDP packets to listening ports, aka Bug ID CSCue69413.
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Analysis
by VulDB Data Team • 05/26/2021
The vulnerability described in CVE-2013-5503 represents a critical memory management flaw within Cisco IOS XR software version 4.3.1, specifically affecting the UDP processing functionality. This issue manifests when the system encounters full packet queues during UDP packet handling, where the operating system fails to properly release allocated memory resources. The flaw operates at the network operating system level, impacting the routing and switching capabilities of Cisco devices running this particular software version. The vulnerability is particularly concerning as it can be exploited remotely through carefully crafted UDP packet sequences directed at listening ports on affected devices, creating a persistent memory consumption attack vector.
The technical implementation of this vulnerability stems from improper memory deallocation mechanisms within the UDP processing module of the IOS XR operating system. When packet queues reach their maximum capacity, the system should automatically release the memory associated with discarded packets to maintain optimal resource utilization. However, the flaw causes the system to retain memory references even after packet processing completes, leading to progressive memory exhaustion over time. This behavior creates a memory leak condition that can be systematically exploited by attackers who send UDP packets to targeted listening ports, causing the device to consume increasing amounts of memory until system stability is compromised. The vulnerability specifically affects the packet queue management logic and demonstrates a failure in proper resource cleanup procedures.
The operational impact of CVE-2013-5503 extends beyond simple service disruption to potentially compromise the entire network infrastructure relying on affected Cisco devices. Remote attackers can leverage this vulnerability to perform sustained denial of service attacks against network services, routing protocols, and management interfaces. The memory consumption occurs gradually but persistently, making it difficult to detect and mitigate without proper monitoring. Network administrators may observe decreasing system performance, increased memory utilization, and eventual device instability or complete service failure. This vulnerability particularly affects network devices serving as core routers, firewalls, or other critical infrastructure components where continuous availability is essential for network operations.
Mitigation strategies for this vulnerability should include immediate software patching to address the memory management flaw in IOS XR 4.3.1. Cisco released security advisories and software updates specifically addressing this issue, which should be deployed across all affected network devices. Network segmentation and access control measures can provide temporary protection by limiting exposure to external UDP traffic on critical ports. Implementing rate limiting and packet filtering rules to restrict UDP traffic to essential services can reduce attack surface. Monitoring systems should be configured to track memory utilization patterns and alert administrators to unusual consumption trends. Additionally, network administrators should consider implementing redundant systems and failover mechanisms to maintain service availability during potential exploitation attempts. This vulnerability aligns with CWE-401, which describes improper release of memory resources, and maps to ATT&CK technique T1499.004 for network denial of service attacks.