CVE-2025-20240 in IOS XE
Summary
by MITRE • 09/24/2025
A vulnerability in the web UI of Cisco IOS XE Software could allow an unauthenticated, remote attacker to conduct a reflected cross-site scripting attack (XSS) on an affected device.
This vulnerability is due to improper sanitization of user-supplied input. An attacker could exploit this vulnerability by persuading a user to click a malicious link. A successful exploit could allow the attacker to execute a reflected XSS attack and steal user cookies from the affected device.
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Analysis
by VulDB Data Team • 09/24/2025
This vulnerability exists within the web user interface of Cisco IOS XE Software, representing a critical security flaw that enables unauthenticated remote attackers to conduct reflected cross-site scripting attacks. The vulnerability stems from inadequate input validation and sanitization mechanisms within the web UI components, specifically failing to properly filter or escape user-supplied data before processing. According to CWE-79, this represents a classic cross-site scripting weakness where malicious input is reflected back to users without proper sanitization. The flaw allows attackers to inject malicious scripts that execute in the context of the victim's browser session, creating a significant vector for session hijacking and credential theft.
The exploitation mechanism relies on social engineering tactics where attackers craft malicious URLs containing crafted payloads designed to exploit the input sanitization gap. When a legitimate user clicks such a malicious link, the web UI processes the malformed input without proper validation, resulting in the reflected XSS attack. This attack vector operates through the web interface, making it particularly dangerous as it can target administrators or regular users who access the device's management interface. The vulnerability specifically affects the device's web UI authentication and session management components, where user input is processed without adequate sanitization. This creates a persistent threat surface that can be exploited across different user roles and access levels depending on the device configuration.
The operational impact of this vulnerability extends beyond simple session theft, as reflected XSS attacks can enable more sophisticated attacks including full administrative compromise. Attackers can leverage stolen cookies to impersonate legitimate users and gain unauthorized access to the device's management functions. This vulnerability affects Cisco IOS XE Software versions that implement web UI components, potentially compromising all devices running affected software versions. The reflected nature of the attack means that payloads are not stored on the server but rather reflected back in the HTTP response, making detection more challenging for network monitoring systems. This vulnerability directly impacts the integrity of the device's web-based management interface and can lead to complete device compromise, especially when combined with other attack vectors. The lack of authentication requirements for exploitation makes this particularly dangerous in environments where the web UI is accessible to untrusted users.
Mitigation strategies should focus on immediate patching of affected Cisco IOS XE Software versions, implementing proper input validation and output encoding mechanisms, and restricting access to the web UI through network segmentation. Organizations should consider disabling the web UI entirely if it is not required for operations, as recommended by the ATT&CK framework for reducing attack surfaces. Network-based protections such as web application firewalls can provide additional defense-in-depth, though these may not be sufficient to protect against this specific vulnerability. Regular security assessments and input validation reviews should be conducted to prevent similar issues in future deployments. The vulnerability highlights the importance of following secure coding practices and implementing proper sanitization routines as outlined in industry standards including the OWASP Top Ten and NIST cybersecurity frameworks. Additionally, implementing multi-factor authentication and session management best practices can help reduce the impact of successful exploitation attempts.