CVE-2024-20455 in IOS XE Catalyst SD-WAN
Summary
by MITRE • 09/25/2024
A vulnerability in the process that classifies traffic that is going to the Unified Threat Defense (UTD) component of Cisco IOS XE Software in controller mode could allow an unauthenticated, remote attacker to cause a denial of service (DoS) condition on an affected device.
This vulnerability exists because UTD improperly handles certain packets as those packets egress an SD-WAN IPsec tunnel. An attacker could exploit this vulnerability by sending crafted traffic through an SD-WAN IPsec tunnel that is configured on an affected device. A successful exploit could allow the attacker to cause the device to reload, resulting in a DoS condition. Note: SD-WAN tunnels that are configured with Generic Routing Encapsulation (GRE) are not affected by this vulnerability.
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Analysis
by VulDB Data Team • 01/07/2025
The vulnerability described in CVE-2024-20455 represents a critical denial of service weakness within Cisco IOS XE Software's Unified Threat Defense component when operating in controller mode. This flaw specifically manifests in the traffic classification process that governs data flowing through SD-WAN IPsec tunnels, creating an avenue for remote attackers to disrupt network operations without requiring authentication credentials. The affected software component processes network traffic through a complex tunneling mechanism that involves IPsec encryption and SD-WAN protocols, making this vulnerability particularly concerning for enterprise networks that rely heavily on secure tunneling for connectivity between branch offices and central data centers.
The technical root cause of this vulnerability stems from improper packet handling within the UTD module's traffic classification logic when packets traverse SD-WAN IPsec tunnels. When crafted malicious packets are transmitted through these tunnels, the system fails to properly validate or process the traffic flow, leading to a system crash or unexpected restart condition. This improper handling occurs during the egress processing phase of the tunneling mechanism, where the device's internal state becomes corrupted due to malformed packet structures or unexpected sequence values that the UTD component cannot properly classify or route. The vulnerability specifically targets the interaction between the UTD traffic classification engine and the SD-WAN tunneling infrastructure, creating a condition where legitimate network operations are disrupted by malicious packet sequences.
The operational impact of this vulnerability extends beyond simple service interruption, as it can result in complete device reloads that may take considerable time to recover from, potentially disrupting critical network services for extended periods. Network administrators face the challenge of maintaining service availability while the device undergoes restart procedures, which can affect multiple network segments depending on the device's role within the SD-WAN architecture. Organizations utilizing Cisco IOS XE Software in controller mode for their SD-WAN deployments are particularly vulnerable, as the attack can be executed remotely without requiring physical access or network credentials, making it an attractive vector for threat actors seeking to disrupt business operations. The DoS condition can occur at any time during active tunnel operations, potentially coinciding with critical business hours or network maintenance windows, amplifying the operational disruption.
Mitigation strategies for CVE-2024-20455 should focus on immediate network segmentation and traffic filtering to prevent exploitation while more comprehensive solutions are implemented. Network administrators should consider implementing access control lists or firewall rules that filter suspicious traffic patterns through SD-WAN tunnels, particularly targeting the specific packet structures that trigger the vulnerability. The Cisco IOS XE Software update released in response to this vulnerability addresses the root cause by improving packet validation and classification logic within the UTD component, ensuring proper handling of edge cases in tunnel egress processing. Organizations should also implement monitoring solutions that can detect unusual traffic patterns or device restart events that may indicate exploitation attempts, as the vulnerability may be used as part of broader attack campaigns targeting network infrastructure. This vulnerability aligns with CWE-121, which addresses stack-based buffer overflow conditions, and may map to ATT&CK technique T1499.004 for network disruption attacks through service availability compromise. The affected SD-WAN GRE tunnels are not impacted, which provides a temporary workaround for organizations that can reconfigure their network architecture to utilize GRE instead of IPsec for specific connections while awaiting full patch deployment.