CVE-2011-3277 in IOS
Summary
by MITRE
Unspecified vulnerability in the NAT implementation in Cisco IOS 12.1 through 12.4 and 15.0 through 15.1, and IOS XE 3.1.xSG, allows remote attackers to cause a denial of service (device reload) by sending crafted H.323 packets to TCP port 1720, aka Bug ID CSCth11006.
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Analysis
by VulDB Data Team • 11/23/2021
The vulnerability described in CVE-2011-3277 represents a critical flaw in Cisco IOS network operating system implementations that affects multiple version ranges including IOS 12.1 through 12.4, 15.0 through 15.1, and IOS XE 3.1.xSG releases. This issue specifically targets the Network Address Translation (NAT) functionality within the IOS stack, creating a pathway for remote attackers to execute denial of service attacks against affected network devices. The vulnerability manifests when the system receives specially crafted H.323 packets on TCP port 1720, which is the standard port used for H.323 signaling in VoIP communications. The flaw was identified and documented under Bug ID CSCth11006, indicating its recognition within Cisco's internal vulnerability tracking systems.
The technical nature of this vulnerability stems from insufficient input validation within the NAT processing module when handling H.323 protocol traffic. When the affected IOS versions receive malformed or specially constructed H.323 packets on the designated port, the NAT implementation fails to properly handle the packet processing, leading to a system crash or device reload. This occurs because the NAT engine does not adequately sanitize or validate the incoming packet headers and payload data before attempting to translate addresses or process the signaling information. The vulnerability exploits a buffer handling or state management issue within the NAT subsystem that causes the device to enter an unstable state, ultimately resulting in a complete system restart. This behavior aligns with CWE-121, which describes heap-based buffer overflow conditions, and CWE-122, which covers buffer overflow vulnerabilities in heap-based memory management.
The operational impact of this vulnerability extends beyond simple service disruption, as it can affect critical network infrastructure components that rely on NAT functionality for traffic management and security enforcement. Network administrators operating affected Cisco devices face the risk of unauthorized actors causing intentional outages that could disrupt voice communications, data services, or other network functions that depend on the affected NAT implementation. The remote nature of the attack means that adversaries do not require physical access or local network credentials to exploit the vulnerability, making it particularly dangerous for publicly accessible network equipment. Organizations with multiple affected devices across their network infrastructure could experience cascading failures if the attack targets core routing or security appliances. The vulnerability also impacts the availability aspect of the CIA triad, as it directly compromises the availability of network services by forcing device restarts.
Mitigation strategies for CVE-2011-3277 should focus on both immediate defensive measures and long-term architectural improvements. Network administrators should implement access control lists to block traffic on TCP port 1720 from untrusted sources, effectively preventing the attack vectors that exploit this vulnerability. Cisco recommends upgrading affected IOS versions to patched releases that contain fixes for the NAT implementation flaws. The organization should also consider implementing intrusion detection systems that can identify and alert on suspicious H.323 traffic patterns, providing additional layers of defense. Network segmentation strategies can help limit the impact scope by isolating critical network segments from potentially compromised devices. The mitigation approach aligns with ATT&CK technique T1499.004, which involves network disruption through denial of service attacks, and T1566.001, which addresses social engineering through spearphishing. Regular security assessments and vulnerability scanning should be conducted to identify any remaining instances of affected software versions, while maintaining updated patch management processes to ensure all network devices remain protected against similar vulnerabilities.