CVE-2026-20311 in IOS XE Software
Summary
by MITRE • 08/05/2026
A vulnerability in the web-based management interface of Cisco IOS XE Software could allow an authenticated, remote attacker with low privileges to cause a denial of service (DoS) condition on an affected device.
This vulnerability is due to insufficient error handling in the web-based management interface. An attacker could exploit this vulnerability by authenticating with a malformed certificate. A successful exploit could allow the attacker to cause the affected device to reload, resulting in a DoS condition.
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Analysis
by VulDB Data Team • 08/05/2026
This vulnerability resides within the web-based management interface of Cisco IOS XE Software, representing a significant security weakness that can be exploited by authenticated attackers with minimal privileges. The flaw stems from inadequate error handling mechanisms that fail to properly validate and process authentication requests. According to CWE-20, this represents a classic input validation issue where the system does not adequately sanitize or verify malformed inputs before processing them. The vulnerability specifically targets the certificate authentication mechanism, making it particularly dangerous as it can be exploited by attackers who have already gained some level of access to the system.
The technical exploitation of this vulnerability requires an attacker to authenticate using a malformed certificate, which then triggers the insufficient error handling within the web interface. This type of attack pattern aligns with ATT&CK technique T1078.004, which covers valid accounts used for lateral movement and privilege escalation. When the malformed certificate is processed, the system fails to properly handle the error condition, leading to an uncontrolled application state that ultimately results in device restart or reload. The DoS condition affects the availability of critical network infrastructure, potentially disrupting business operations and network connectivity.
The operational impact of this vulnerability extends beyond simple service disruption as it can be leveraged by attackers to repeatedly cause device outages, creating a persistent threat to network reliability. Network administrators may find themselves unable to access affected devices through their web interfaces during an attack, forcing them to rely on alternative management methods such as console access or SSH connections. This vulnerability particularly affects enterprise networks where centralized management through web interfaces is common, and the ability to cause repeated reloads can be used to create sustained disruption.
Mitigation strategies should focus on implementing proper input validation and error handling mechanisms within the web interface components of IOS XE Software. Cisco has released patches addressing this vulnerability, emphasizing the importance of timely software updates and security maintenance. Network administrators should also implement monitoring solutions that can detect unusual authentication patterns or repeated connection attempts that might indicate exploitation attempts. Additionally, implementing network segmentation and access controls can limit the potential impact of such attacks by reducing the attack surface available to authenticated but malicious users. The vulnerability demonstrates the critical importance of robust error handling in network management interfaces, as even seemingly minor flaws in input validation can lead to significant availability impacts.