CVE-2015-0688 in IOS XE
Summary
by MITRE
Cisco IOS XE 3.10.2S on an ASR 1000 device with an Embedded Services Processor (ESP) module, when NAT is enabled, allows remote attackers to cause a denial of service (module crash) via malformed H.323 packets, aka Bug ID CSCup21070.
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Analysis
by VulDB Data Team • 05/02/2022
The vulnerability identified as CVE-2015-0688 represents a critical denial of service flaw affecting Cisco IOS XE 3.10.2S running on ASR 1000 series devices equipped with Embedded Services Processor modules. This weakness specifically manifests when Network Address Translation (NAT) functionality is active, creating a pathway for remote attackers to exploit the system through crafted H.323 protocol packets. The issue stems from insufficient input validation within the ESP module's handling of H.323 traffic, which constitutes a fundamental security oversight in the network infrastructure software stack. The vulnerability operates at the protocol processing layer where malformed H.323 packets can trigger memory corruption or buffer overflow conditions that ultimately lead to the complete crash of the ESP module.
The technical exploitation of this vulnerability leverages the H.323 protocol implementation within the IOS XE operating system to craft packets that contain malformed data structures or unexpected field values. When the ESP module processes these malicious packets, the insufficient validation mechanisms fail to properly sanitize the input, causing the system to enter an unstable state that results in an immediate module crash. This behavior aligns with CWE-121, which describes stack-based buffer overflow conditions, and CWE-122, which addresses heap-based buffer overflow scenarios. The attack vector requires only network access to the affected device, making it particularly dangerous as it can be executed remotely without authentication credentials, representing a significant risk to network availability and service continuity.
The operational impact of CVE-2015-0688 extends beyond simple service disruption to encompass broader network reliability concerns. When the ESP module crashes, it affects not only the NAT functionality but also any other services dependent on the module, including voice services that rely on H.323 signaling protocols. The module restart process introduces additional downtime and potential data loss, particularly in mission-critical environments where continuous network availability is essential. This vulnerability directly impacts the availability component of the CIA triad and can be classified under the ATT&CK technique T1499.1, which describes the use of network denial of service methods to disrupt services. The affected ASR 1000 series devices represent core network infrastructure elements that typically serve as routing and switching points, making this vulnerability particularly dangerous for enterprise and service provider networks.
Cisco's official bug identification CSCup21070 documents the specific conditions under which this vulnerability manifests, emphasizing that the issue is specifically tied to the interaction between NAT functionality and H.323 packet processing within the ESP module. The vulnerability affects only devices running IOS XE 3.10.2S with NAT enabled, which creates a targeted attack surface for threat actors seeking to disrupt network services. Organizations should consider implementing network segmentation strategies to isolate affected devices and reduce the potential blast radius of such attacks. The recommended mitigation approach includes applying the appropriate Cisco security patches and updates that address the input validation deficiencies in the H.323 processing code. Additionally, network administrators should consider disabling NAT functionality on affected devices if it is not essential for business operations, and implementing network monitoring to detect anomalous H.323 traffic patterns that could indicate exploitation attempts. The vulnerability demonstrates the importance of proper input validation and the potential for protocol-specific flaws to create cascading failures in network infrastructure components.