CVE-2020-3337 in Umbrella
Summary
by MITRE
A vulnerability in the web server of Cisco Umbrella could allow an unauthenticated, remote attacker to redirect a user to an undesired web page. The vulnerability is due to improper input validation of the URL parameters in an HTTP request that is sent to an affected device. An attacker could exploit this vulnerability by sending a crafted HTTP request that could cause the web application to redirect the request to a specified malicious URL. A successful exploit could allow the attacker to redirect a user to a malicious website.
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Analysis
by VulDB Data Team • 10/25/2020
The vulnerability identified as CVE-2020-3337 represents a critical security flaw in Cisco Umbrella's web server component that exposes organizations to sophisticated phishing and man-in-the-middle attack vectors. This weakness resides within the application's handling of HTTP request parameters, specifically failing to properly validate URL inputs that are processed by the web server interface. The vulnerability affects Cisco Umbrella's cloud security platform, which serves as a critical component for enterprise network protection and threat intelligence. Organizations relying on this service for DNS-level security and threat prevention face significant risk when this vulnerability remains unaddressed. The flaw demonstrates a fundamental failure in input sanitization practices that directly impacts the integrity of user navigation and security policies. The vulnerability exists in the web server's request processing logic where user-supplied URL parameters are not adequately validated before being used in redirection operations. This creates a pathway for attackers to manipulate the application's behavior through crafted HTTP requests that exploit the insufficient validation mechanisms.
The technical exploitation of CVE-2020-3337 follows a well-established pattern that aligns with common web application attack methodologies. Attackers can craft malicious HTTP requests containing specially formatted URL parameters that bypass the web server's input validation checks. When the web server processes these requests, it fails to properly sanitize the input data, allowing the malicious parameters to be interpreted as legitimate redirection instructions. The vulnerability specifically targets the URL parameter handling within HTTP requests sent to the affected Cisco Umbrella web server, creating a condition where user requests can be transparently redirected to attacker-controlled domains without authentication requirements. This type of vulnerability is classified as a web application vulnerability that falls under the broader category of insecure input handling and improper validation. The attack vector requires no authentication credentials and can be executed remotely, making it particularly dangerous for organizations that rely on the service for critical network security functions. The flaw essentially allows for arbitrary redirection attacks that could be used to deliver malware, conduct phishing campaigns, or redirect users to compromised domains.
The operational impact of this vulnerability extends far beyond simple redirection capabilities and represents a serious threat to enterprise security posture and user safety. Organizations using Cisco Umbrella for DNS-level security protection face potential exposure to sophisticated attack chains where legitimate security controls are bypassed through this vulnerability. Users who encounter malicious redirects could be directed to phishing sites that attempt to harvest credentials, install malware, or conduct social engineering attacks against the organization's workforce. The vulnerability undermines the trust model that Cisco Umbrella establishes for network security, as it allows attackers to subvert the intended security controls that protect users from malicious websites. Additionally, the vulnerability could be leveraged in conjunction with other attack vectors to create more sophisticated multi-stage attacks that exploit the compromised web server as an initial access point. The redirection capability provides attackers with a mechanism to establish persistent access to user systems through malicious website delivery, potentially leading to broader compromise of enterprise networks and data breaches.
Organizations should implement immediate mitigation strategies to address this vulnerability, including applying the relevant Cisco security patches and updates as released through the official Cisco Security Advisory channels. Network administrators should also consider implementing additional monitoring and detection measures to identify potential exploitation attempts through unusual HTTP request patterns or unexpected redirection behaviors. The vulnerability's classification under CWE-20, which covers "Improper Input Validation," indicates that the fix should involve implementing robust input sanitization and validation mechanisms. Organizations may also want to consider network-level controls such as web application firewalls or proxy configurations that can help detect and block malicious redirection attempts. The ATT&CK framework categorizes this vulnerability under T1566, which covers "Phishing" techniques, highlighting the potential for this flaw to enable social engineering attacks. Security teams should also review their incident response procedures to ensure readiness for potential exploitation of this vulnerability, as it represents a clear threat to user safety and organizational security. The remediation process should include thorough testing of the patched web server components to ensure that the input validation improvements are properly implemented and that no regressions have been introduced in the service's core functionality.