CVE-2011-2578 in IOS
Summary
by MITRE
Memory leak in Cisco IOS 15.1 and 15.2 allows remote attackers to cause a denial of service (memory consumption) via malformed SIP packets on a NAT interface, aka Bug ID CSCts12366.
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Analysis
by VulDB Data Team • 12/01/2021
The vulnerability described in CVE-2011-2578 represents a critical memory leak issue affecting Cisco IOS versions 15.1 and 15.2 operating on network address translation interfaces. This flaw specifically targets Session Initiation Protocol handling within the Cisco IOS operating system, creating a remote denial of service condition that can be exploited by attackers without authentication. The vulnerability manifests when malformed SIP packets are transmitted through a NAT interface, causing the affected device to consume excessive memory resources over time until system stability is compromised.
The technical root cause of this memory leak stems from insufficient input validation within the SIP processing module of Cisco IOS. When the system encounters malformed SIP packets, the parsing routine fails to properly handle the malformed data structures, leading to memory allocation without subsequent deallocation. This memory consumption pattern is particularly concerning because it occurs during normal network operations when the device is processing legitimate traffic through NAT interfaces. The flaw is classified under CWE-401 as a failure to release memory resources, which directly aligns with the memory leak characteristics observed in this vulnerability. The issue is further exacerbated by the fact that the memory consumption is gradual and persistent, making it difficult to detect through simple monitoring while still effectively degrading system performance.
The operational impact of this vulnerability extends beyond simple service disruption to potentially compromise network infrastructure reliability. Network administrators may observe gradual performance degradation, increased memory utilization, and eventual system instability or complete service outages. Attackers can leverage this vulnerability to conduct sustained denial of service attacks by continuously sending malformed SIP packets, forcing the target device to allocate memory resources indefinitely. This vulnerability particularly affects enterprise networks and service providers that rely on SIP for voice over IP communications, as NAT interfaces are commonly used to translate between private and public network addresses. The attack can be executed remotely without requiring any authentication credentials, making it especially dangerous in environments where network security controls may not adequately protect against such attacks.
Mitigation strategies for this vulnerability should include immediate deployment of Cisco IOS patches and updates that address the memory leak in SIP packet processing. Network administrators should implement access control lists to filter malformed SIP traffic at network boundaries and consider disabling SIP processing on NAT interfaces when not strictly necessary. The implementation of network monitoring solutions that can detect unusual memory consumption patterns and sudden increases in memory utilization provides early warning capabilities. Organizations should also consider deploying intrusion detection systems that can identify and alert on malformed SIP packet patterns that match the vulnerability characteristics. From an operational security perspective, implementing proper network segmentation and limiting SIP traffic to trusted network segments reduces the attack surface. The vulnerability's characteristics align with ATT&CK technique T1499.004 for resource exhaustion attacks, and network defenders should consider implementing defensive measures that align with the MITRE ATT&CK framework's approach to mitigating resource exhaustion threats. Regular security assessments and vulnerability scanning should include verification of IOS versions and patch status to prevent exploitation of this and similar memory leak vulnerabilities.