CVE-2020-3516 in IOS XE
Summary
by MITRE
A vulnerability in the web server authentication of Cisco IOS XE Software could allow an authenticated, remote attacker to crash the web server on the device. The vulnerability is due to insufficient input validation during authentication. An attacker could exploit this vulnerability by entering unexpected characters during a valid authentication. A successful exploit could allow the attacker to crash the web server on the device, which must be manually recovered by disabling and re-enabling the web server.
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Analysis
by VulDB Data Team • 09/25/2020
The vulnerability identified as CVE-2020-3516 resides within Cisco IOS XE Software's web server authentication mechanism, representing a critical security weakness that undermines the integrity of network device access controls. This flaw manifests as insufficient input validation during the authentication process, creating an exploitable condition that allows authenticated remote attackers to disrupt web server operations. The vulnerability specifically targets the web server component of Cisco IOS XE devices, which serves as the primary interface for administrative access and configuration management. Organizations relying on these devices for network infrastructure management face significant operational risks when this vulnerability remains unaddressed, as it directly impacts the availability and reliability of critical network services.
The technical exploitation of CVE-2020-3516 occurs when an authenticated attacker inputs unexpected or malformed characters during the authentication process, triggering a failure in the web server's input validation routines. This insufficient validation allows the attacker to craft malicious authentication requests that cause the web server to crash and become unresponsive. The vulnerability stems from the absence of proper sanitization and validation of user inputs, which is a fundamental security principle that should prevent malformed data from causing system instability. According to CWE classification, this represents a variant of CWE-20: Improper Input Validation, which is a well-documented weakness that frequently leads to various security issues including denial of service conditions. The specific nature of the flaw allows an attacker to leverage legitimate authentication credentials to gain the ability to disrupt services rather than simply access data, making it particularly concerning for network administrators.
The operational impact of this vulnerability extends beyond simple service disruption, as it creates a scenario where network administrators must manually intervene to restore web server functionality. This manual recovery process introduces significant downtime and operational overhead, particularly in environments where continuous network availability is critical for business operations. The vulnerability affects Cisco IOS XE Software versions that include the web server component, potentially impacting a wide range of network infrastructure devices including routers, switches, and other network appliances that utilize this software platform. From an ATT&CK framework perspective, this vulnerability aligns with the T1499.004 technique related to Network Denial of Service, where adversaries leverage software weaknesses to disrupt network services and potentially gain further access to compromised systems. The requirement for manual intervention to restore functionality also increases the risk of human error during recovery operations, potentially leading to extended outages or misconfiguration issues.
Mitigation strategies for CVE-2020-3516 should prioritize immediate patch deployment from Cisco, as the vulnerability requires software updates to address the underlying input validation flaws. Network administrators should implement network segmentation and access controls to limit the potential attack surface, reducing the likelihood of unauthorized access to devices running vulnerable software versions. The implementation of monitoring solutions that can detect unusual authentication patterns or web server behavior changes provides early warning capabilities for potential exploitation attempts. Additionally, organizations should consider disabling unnecessary web server functionality when not actively required for administration purposes, reducing the attack surface available to potential attackers. Regular security assessments and vulnerability scanning should be conducted to identify other potential weaknesses in the network infrastructure that could be exploited in conjunction with this vulnerability. The remediation process must also include comprehensive testing of patched software in controlled environments before deployment to production systems to ensure that updates do not introduce compatibility issues or additional operational risks.