CVE-2018-0476 in IOS XE
Summary
by MITRE
A vulnerability in the Network Address Translation (NAT) Session Initiation Protocol (SIP) Application Layer Gateway (ALG) of Cisco IOS XE Software could allow an unauthenticated, remote attacker to cause an affected device to reload. The vulnerability is due to improper processing of SIP packets in transit while NAT is performed on an affected device. An unauthenticated, remote attacker could exploit this vulnerability by sending crafted SIP packets via UDP port 5060 through an affected device that is performing NAT for SIP packets. A successful exploit could allow an attacker to cause the device to reload, resulting in a denial of service (DoS) condition.
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Analysis
by VulDB Data Team • 05/22/2023
The vulnerability identified as CVE-2018-0476 resides within the Network Address Translation Session Initiation Protocol Application Layer Gateway functionality of Cisco IOS XE Software, representing a critical weakness that enables remote attackers to induce device reloads without authentication. This flaw specifically manifests in the improper handling of SIP packets during NAT processing, creating a pathway for malicious actors to disrupt network operations through deliberate system reloads.
The technical exploitation of this vulnerability occurs through the manipulation of Session Initiation Protocol packets transmitted over UDP port 5060, which serves as the standard communication port for SIP signaling in VoIP environments. When an affected Cisco device performs NAT operations on SIP traffic, the ALG component fails to properly validate and process incoming SIP packets, leading to a condition where malformed or specially crafted packets can trigger a system reboot. The vulnerability stems from insufficient input validation within the SIP ALG module, which lacks proper boundary checks and packet integrity verification mechanisms. This weakness allows attackers to construct packets that exploit memory handling errors or state management flaws within the NAT-SIP processing pipeline.
The operational impact of CVE-2018-0476 extends beyond simple service disruption, as the device reload caused by this vulnerability can result in complete network outages for VoIP services and potentially affect other network functions that rely on the affected device's routing capabilities. Organizations utilizing Cisco IOS XE devices in environments where SIP traffic flows through NAT configurations face significant risk, particularly in enterprise networks where VoIP systems are prevalent. The DoS condition created by this vulnerability can persist until manual intervention occurs, potentially causing cascading failures in communications infrastructure and impacting business continuity. Network administrators may experience challenges in troubleshooting since the reload behavior can obscure the root cause of service disruptions, requiring detailed packet analysis and system monitoring to identify the attack vector.
Mitigation strategies for this vulnerability should focus on immediate patch application through Cisco's security advisories, which typically provide firmware updates addressing the specific processing flaws in the SIP ALG implementation. Network segmentation and access control measures can help reduce exposure by limiting direct access to affected devices from untrusted networks, while monitoring systems should be deployed to detect anomalous SIP traffic patterns that may indicate exploitation attempts. The vulnerability aligns with CWE-129, which addresses improper validation of input boundaries, and maps to ATT&CK technique T1499.004 for network disruption through service availability attacks. Organizations should also consider implementing rate limiting for SIP traffic and configuring firewalls to restrict UDP port 5060 access to trusted sources only, while maintaining comprehensive logging and alerting mechanisms to detect potential exploitation attempts.