CVE-2015-6271 in IOS XE
Summary
by MITRE
Cisco IOS XE 2.1.0 through 2.4.3 and 2.5.0 on ASR 1000 devices, when NAT Application Layer Gateway is used, allows remote attackers to cause a denial of service (Embedded Services Processor crash) via a crafted SIP packet, aka Bug IDs CSCta74749 and CSCta77008.
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Analysis
by VulDB Data Team • 06/13/2022
The vulnerability described in CVE-2015-6271 represents a critical denial of service flaw affecting Cisco IOS XE software versions 2.1.0 through 2.4.3 and 2.5.0 on ASR 1000 series routers. This issue specifically manifests when the NAT Application Layer Gateway feature is enabled, creating a pathway for remote attackers to disrupt network services through carefully crafted SIP packets. The flaw impacts the Embedded Services Processor which handles various network functions including application layer processing, making it a particularly dangerous vulnerability given the central role these processors play in router operations.
The technical mechanism behind this vulnerability involves a buffer overflow or memory corruption issue within the SIP processing module of the Embedded Services Processor when handling malformed or specially crafted SIP packets. When such packets are received through the NAT Application Layer Gateway, the processor fails to properly validate input data, leading to an unexpected crash that results in complete service disruption. This behavior aligns with CWE-121, which describes stack-based buffer overflow conditions, and CWE-125, which covers out-of-bounds read vulnerabilities that can lead to system instability. The vulnerability demonstrates how application layer processing can introduce critical failure points when input validation is insufficient.
The operational impact of this vulnerability extends beyond simple service interruption, as it affects network infrastructure reliability and availability. Network administrators managing ASR 1000 devices with NAT Application Layer Gateway enabled face significant risk of unauthorized service disruption, potentially affecting voice over IP communications and other SIP-based services. The remote nature of the attack means that adversaries can exploit this vulnerability from outside the network perimeter without requiring physical access or elevated privileges, making it particularly concerning for enterprise and service provider networks. This vulnerability directly maps to ATT&CK technique T1499.004, which covers network disruption through denial of service attacks, and represents a critical weakness in the network infrastructure's resilience.
Mitigation strategies for this vulnerability require immediate attention from network administrators, including applying the relevant Cisco security patches and updates that address the specific buffer overflow conditions in the SIP processing module. Organizations should also consider disabling the NAT Application Layer Gateway feature on affected devices until proper patches can be deployed, particularly in environments where the feature is not essential for operations. Network segmentation and monitoring can help detect unusual SIP traffic patterns that might indicate exploitation attempts, while implementing rate limiting on SIP traffic can reduce the effectiveness of potential attacks. The vulnerability highlights the importance of maintaining up-to-date security patches and proper input validation in embedded systems, especially those handling network protocol processing. Additionally, organizations should conduct thorough vulnerability assessments of their network infrastructure to identify similar issues in other Cisco products and ensure comprehensive security coverage across all network devices.