CVE-2005-4794 in Host
Summary
by MITRE
Cisco IP Phones 7902/7905/7912, ATA 186/188, Unity Express, ACNS, and Subscriber Edge Services Manager (SESM) allows remote attackers to cause a denial of service (crash or instability) via a compressed DNS packet with a label length byte with an incorrect offset.
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Analysis
by VulDB Data Team • 11/23/2024
The vulnerability identified as CVE-2005-4794 represents a critical denial of service flaw affecting multiple Cisco IP phone models including 7902, 7905, and 7912, along with ATA 186/188 devices, Unity Express systems, ACNS platforms, and Subscriber Edge Services Manager components. This weakness stems from improper handling of compressed DNS packets within the network infrastructure devices, specifically when processing label length bytes that contain incorrect offset values. The flaw operates at the network protocol level, exploiting the DNS resolution mechanism that these voice-enabled devices rely upon for proper operation and communication within enterprise networks.
The technical implementation of this vulnerability involves the processing of DNS compression pointers within the Resource Record data structures. When a Cisco IP phone or related device receives a malformed DNS packet containing a label length byte with an incorrect offset, the device's DNS resolver engine fails to properly handle the malformed data structure. This improper handling causes the device to crash or become unstable, resulting in complete service disruption. The vulnerability is particularly concerning because it affects devices that are critical to enterprise communications infrastructure, where availability and reliability are paramount. The flaw manifests as a buffer over-read condition or improper pointer arithmetic when the device attempts to decompress the DNS labels, leading to memory corruption and system instability.
The operational impact of this vulnerability extends beyond simple service interruption, as it can affect entire communication networks that depend on these devices for voice services. Enterprise organizations utilizing Cisco IP phones and related infrastructure may experience complete loss of telephony services, potentially affecting business operations and emergency communication capabilities. The remote nature of the attack means that malicious actors can exploit this vulnerability from external network locations without requiring physical access or authentication credentials. This makes the vulnerability particularly dangerous in environments where network security controls may not adequately protect voice infrastructure components from external threats. The vulnerability affects devices that are typically deployed in mission-critical environments where downtime can result in significant financial and operational consequences, making this a high-priority security concern for enterprise network administrators.
Mitigation strategies for CVE-2005-4794 should focus on network segmentation and access control measures to limit exposure of vulnerable devices to untrusted network traffic. Implementing DNS filtering mechanisms and deploying network intrusion prevention systems can help detect and block malicious DNS packets before they reach affected devices. Cisco has released patches and firmware updates that address the DNS processing flaw by implementing proper validation of label length bytes and offset values in compressed DNS records. Network administrators should prioritize applying these security updates to all affected devices and consider implementing network monitoring solutions to detect anomalous DNS traffic patterns that may indicate exploitation attempts. The vulnerability aligns with CWE-129, which addresses improper validation of input bounds, and can be mapped to ATT&CK technique T1499.002 for network denial of service attacks, emphasizing the need for comprehensive network security controls to protect voice infrastructure components from similar vulnerabilities.