CVE-2008-3811 in IOS
Summary
by MITRE
Cisco IOS 12.2 and 12.4, when NAT Skinny Call Control Protocol (SCCP) Fragmentation Support is enabled, allows remote attackers to cause a denial of service (device reload) via segmented SCCP messages, aka Cisco Bug ID CSCsi17020, a different vulnerability than CVE-2008-3810.
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Analysis
by VulDB Data Team • 08/17/2019
The vulnerability described in CVE-2008-3811 represents a critical denial of service flaw affecting Cisco IOS versions 12.2 and 12.4 that implement NAT Skinny Call Control Protocol fragmentation support. This vulnerability specifically targets the handling of segmented SCCP messages within the network address translation environment, creating a scenario where remote attackers can exploit the system's processing of fragmented call control packets to trigger complete device reboots. The issue manifests when the Skinny Call Control Protocol is configured with fragmentation support enabled, which is commonly implemented in enterprise voice environments that utilize Cisco's IP Telephony infrastructure. The vulnerability operates through the improper handling of segmented SCCP messages that occur during network address translation processes, where the system fails to properly reconstruct or validate fragmented packets before processing them.
The technical flaw stems from insufficient validation and processing of fragmented SCCP messages within the NAT environment of Cisco IOS routers. When SCCP fragmentation is enabled, the system must reassemble segmented packets before processing them as complete call control messages. However, the vulnerable implementation contains a buffer handling or packet reassembly flaw that occurs specifically when these fragmented messages are processed through NAT translation. The vulnerability is classified under CWE-129 as an insufficient validation of the length of input data, and more specifically relates to CWE-121 which deals with buffer overflow conditions in the context of input validation. This allows attackers to craft specially malformed segmented SCCP messages that, when processed through the NAT translation mechanism, cause the system to enter an unrecoverable state leading to device reload. The flaw essentially represents a failure in the packet reassembly logic that does not properly account for the potential for maliciously crafted fragmented data during the NAT processing phase.
The operational impact of this vulnerability extends beyond simple service disruption to potentially compromise the availability of critical voice communication infrastructure. Organizations relying on Cisco IP Telephony systems that have NAT Skinny Call Control Protocol fragmentation support enabled face significant risk of unauthorized service interruption that can affect business continuity and communication availability. The remote nature of the attack means that adversaries can exploit this vulnerability from outside the network perimeter, making it particularly dangerous for organizations with internet-facing voice infrastructure. The vulnerability affects the core functionality of Cisco routers that handle voice traffic, potentially causing cascading failures in telephony services when multiple devices are compromised. The device reload caused by this vulnerability can result in temporary loss of voice services for the duration of the restart process, and in high-availability environments, could trigger failover mechanisms that disrupt service delivery. This vulnerability is particularly concerning in enterprise environments where voice communication is critical for business operations.
Mitigation strategies for CVE-2008-3811 should focus on immediate configuration changes and network architecture modifications to prevent exploitation. The primary recommendation involves disabling NAT Skinny Call Control Protocol fragmentation support on affected Cisco IOS devices when this functionality is not strictly required for network operations. Organizations should also implement network segmentation and access control measures to limit exposure of voice infrastructure to untrusted networks. The implementation of ingress and egress filtering can help reduce the attack surface by preventing malicious SCCP packets from reaching vulnerable devices. Network administrators should also consider deploying intrusion detection systems that can monitor for anomalous SCCP traffic patterns that may indicate exploitation attempts. Additionally, maintaining current Cisco IOS software versions and applying relevant security patches is essential for long-term protection, as this vulnerability was addressed in subsequent releases of Cisco IOS. The vulnerability aligns with ATT&CK technique T1499.004 which covers network denial of service attacks, and T1566.001 which involves phishing attacks targeting network infrastructure, as the vulnerability can be exploited through network-based attacks that leverage the exposed voice infrastructure.