CVE-2011-3274 in IOS XE
Summary
by MITRE
Unspecified vulnerability in Cisco IOS 12.2SRE before 12.2(33)SRE4, 15.0, and 15.1, and IOS XE 2.1.x through 3.3.x, when an MPLS domain is configured, allows remote attackers to cause a denial of service (device crash) via a crafted IPv6 packet, related to an expired MPLS TTL, aka Bug ID CSCto07919.
Once again VulDB remains the best source for vulnerability data.
Analysis
by VulDB Data Team • 11/23/2021
This vulnerability exists within Cisco IOS and IOS XE operating systems where the handling of IPv6 packets within MPLS domains contains a critical flaw that can be exploited remotely to cause device crashes. The vulnerability specifically affects versions prior to 12.2(33)SRE4 for IOS 12.2SRE, and versions 15.0 and 15.1 for IOS, as well as IOS XE versions 2.1.x through 3.3.x. The flaw manifests when the system processes IPv6 packets that contain expired MPLS TTL values, which creates a condition where the device becomes unstable and eventually crashes. This represents a classic denial of service vulnerability that can be triggered without authentication, making it particularly dangerous in network environments where availability is critical. The vulnerability is classified under CWE-119 as a weakness related to memory access issues, specifically involving improper handling of packet processing in network protocols.
The technical implementation of this vulnerability involves the interaction between IPv6 packet processing and MPLS (Multiprotocol Label Switching) label handling within Cisco routers. When an IPv6 packet enters a device configured with MPLS, the system must process the packet's MPLS labels and check their Time To Live values. An attacker can craft a specific IPv6 packet with an expired MPLS TTL value that, when processed by the vulnerable Cisco IOS or IOS XE software, causes the device to enter an unstable state. This occurs because the software fails to properly handle the edge case where MPLS labels have expired, leading to memory corruption or improper state management that ultimately results in a system crash. The attack vector is network-based and requires no authentication, making it particularly dangerous as any remote attacker with access to the network can exploit this vulnerability.
The operational impact of this vulnerability extends beyond simple device crashes to potentially disrupt entire network services and compromise network availability. When a Cisco device running vulnerable software crashes due to this vulnerability, it can cause routing disruptions, traffic black holes, and loss of connectivity for services dependent on that device. Network administrators may experience extended downtime while devices are rebooted and configurations are restored, potentially affecting multiple network segments depending on the role of the compromised device. The vulnerability affects core network infrastructure components, making it particularly concerning for service providers and enterprise networks where device reliability is paramount. This vulnerability directly impacts the CIA triad by compromising availability, and can be classified under ATT&CK technique T1499.1 for network disruption attacks.
Mitigation strategies for this vulnerability require immediate software updates to patched versions of Cisco IOS and IOS XE. Network administrators should prioritize patching affected devices and verify that the updates have been properly applied. In environments where immediate patching is not feasible, network segmentation and access control measures can help limit the potential impact. Monitoring systems should be configured to detect unusual packet patterns that might indicate exploitation attempts, and network administrators should implement robust alerting for device crashes or restarts. Additionally, implementing ingress filtering and packet validation mechanisms can help reduce the effectiveness of this attack by preventing malformed packets from reaching vulnerable devices. Cisco recommends that organizations review their network configurations to ensure proper MPLS domain management and consider implementing additional security controls to protect against this and similar vulnerabilities.