CVE-2011-3279 in IOS
Summary
by MITRE
The provider-edge MPLS 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) via a malformed SIP packet to UDP port 5060, aka Bug ID CSCti98219.
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Analysis
by VulDB Data Team • 11/23/2021
The vulnerability described in CVE-2011-3279 represents a critical denial of service flaw within Cisco IOS implementations that affect multiple software versions from 12.1 through 12.4 and 15.0 through 15.1, along with IOS XE 3.1.xSG releases. This issue specifically targets the provider-edge MPLS NAT functionality, which is designed to handle network address translation in multiprotocol label switching environments. The flaw manifests when the system receives a malformed Session Initiation Protocol packet destined for the standard UDP port 5060, which is commonly used for VoIP communications and SIP signaling. The vulnerability resides in the packet processing logic of the MPLS NAT implementation, where the system fails to properly validate incoming SIP packets before attempting to process them within the NAT translation context.
The technical exploitation of this vulnerability occurs when an attacker crafts a malformed SIP packet that contains malformed data structures or unexpected packet formats that the Cisco IOS device's MPLS NAT implementation cannot properly handle. This malformed packet is directed toward UDP port 5060, which is the standard port for SIP communications in VoIP environments. When the device receives and attempts to process this malformed packet through its MPLS NAT functionality, the system experiences a critical failure in its packet parsing and translation mechanisms, ultimately leading to a complete device reload or system crash. This behavior constitutes a classic buffer overflow or input validation vulnerability where the system does not adequately sanitize incoming data before processing it within the NAT translation context.
The operational impact of this vulnerability extends beyond simple service disruption as it can affect critical network infrastructure components that rely on MPLS NAT functionality for traffic management and VoIP service delivery. Organizations utilizing affected Cisco IOS versions may experience complete network outages when attackers exploit this vulnerability, particularly in environments where SIP traffic is heavily utilized for voice communications. The vulnerability affects service providers and enterprise networks that deploy MPLS-based services, potentially causing widespread disruption to voice and data services. The device reload caused by this vulnerability means that network services must be manually restored, leading to significant downtime and potential business impact. The vulnerability affects the availability aspect of the CIA triad, specifically targeting the system's ability to maintain continuous operation under attack conditions.
Mitigation strategies for this vulnerability should include immediate software patching and upgrading to Cisco IOS versions that contain the necessary fixes for the MPLS NAT implementation. Network administrators should implement access control lists to filter SIP traffic on UDP port 5060, particularly from untrusted sources, to prevent malformed packets from reaching the vulnerable system. The implementation of network segmentation and firewall rules can provide additional protection layers by limiting direct access to the affected devices from potentially malicious sources. Organizations should also consider implementing intrusion detection systems that can identify and alert on malformed SIP packet patterns that match the vulnerability characteristics. According to CWE standards, this vulnerability maps to CWE-129 Input Validation, and its exploitation aligns with ATT&CK techniques related to denial of service attacks. The vulnerability's classification as a remote attack vector means that network segmentation and proper firewall configuration become essential defensive measures that complement the software patches in providing comprehensive protection against exploitation attempts.