CVE-2016-1361 in IOX XR
Summary
by MITRE
Cisco IOS XR through 4.3.2 on Gigabit Switch Router (GSR) 12000 devices does not properly check for a Bidirectional Forwarding Detection (BFD) header in a UDP packet, which allows remote attackers to cause a denial of service (line-card restart) via a crafted packet, aka Bug ID CSCuw56900.
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Analysis
by VulDB Data Team • 07/10/2022
Cisco IOS XR software running on GSR 12000 series devices contains a critical vulnerability in the Bidirectional Forwarding Detection protocol implementation that enables remote attackers to trigger unauthorized service disruption. The flaw exists within the packet validation mechanism where the system fails to properly verify the presence and integrity of BFD headers within UDP packets destined for the line card processing modules. This oversight allows malicious actors to craft specially formatted packets that bypass normal header validation checks, ultimately causing the affected line cards to restart and interrupt network operations.
The technical nature of this vulnerability stems from insufficient input validation within the network protocol stack of the IOS XR operating system. When the system receives UDP packets containing BFD protocol data, it should validate that proper BFD headers are present before processing the payload. However, the implementation contains a logic flaw where the validation routine does not adequately check for header presence, allowing malformed packets to proceed through the normal processing pipeline. This weakness specifically affects the line card components responsible for forwarding and switching operations, causing them to enter a restart state when encountering the crafted malicious packets.
The operational impact of this vulnerability manifests as a remote denial of service condition that can severely disrupt network infrastructure availability. Attackers can exploit this weakness from remote locations without requiring authentication credentials, making it particularly dangerous for critical network equipment. When successfully exploited, the vulnerability causes line card restarts that result in temporary network outages, service disruption, and potential cascading failures across the affected network segments. The GSR 12000 series devices are commonly deployed in high-availability network environments where such disruptions can have significant business and operational consequences.
This vulnerability aligns with CWE-20, which describes improper input validation in software systems, and represents a classic example of insufficient validation of input data. The attack vector follows the pattern described in the MITRE ATT&CK framework under T1499.004 for network denial of service attacks, where adversaries leverage protocol implementation weaknesses to disrupt services. The vulnerability also demonstrates characteristics of T1566 related to credential harvesting and privilege escalation through network protocol manipulation. Organizations should implement network segmentation and access control measures to limit exposure, while also applying vendor-provided security patches to address the underlying validation flaw in the BFD protocol implementation.
The remediation approach requires immediate deployment of Cisco's security advisories and software updates that correct the BFD header validation logic. Network administrators should also consider implementing network access control lists to filter suspicious UDP traffic containing BFD protocol data, though this represents a temporary mitigation rather than a permanent solution. Additionally, monitoring systems should be configured to detect unusual line card restart patterns that may indicate exploitation attempts, providing early warning capabilities for potential attacks targeting this vulnerability.