CVE-2020-9995 in macOS Server
Summary
by MITRE • 04/03/2021
An issue existed in the parsing of URLs. This issue was addressed with improved input validation. This issue is fixed in macOS Server 5.11. Processing a maliciously crafted URL may lead to an open redirect or cross site scripting.
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Analysis
by VulDB Data Team • 04/03/2021
The vulnerability described represents a critical security flaw in URL parsing mechanisms that could enable attackers to exploit open redirect and cross-site scripting vectors. This issue was specifically addressed in macOS Server version 5.11 through enhanced input validation measures, highlighting the importance of proper URL handling in server-side applications. The vulnerability stems from inadequate validation of user-supplied URL parameters, which can be manipulated to craft malicious inputs that bypass normal security checks. When processing URLs, servers often need to validate and sanitize input to prevent unauthorized redirection or injection attacks that could compromise user sessions or deliver malicious content.
The technical implementation of this vulnerability involves the failure to properly validate URL schemes, hostnames, and path components during parsing operations. Attackers can craft specially formatted URLs that contain unexpected characters or sequences that are not properly escaped or filtered by the application's input validation routines. This weakness creates opportunities for open redirect attacks where users are unknowingly redirected to malicious websites, or cross-site scripting exploitation where attacker-controlled scripts can be injected into web pages viewed by other users. The vulnerability is classified under CWE-601 as an Open Redirect vulnerability and may also relate to CWE-79 for Cross-Site Scripting issues depending on the specific implementation details.
The operational impact of this vulnerability extends beyond simple redirection attacks to potentially enable more sophisticated exploitation techniques that could compromise user data or system integrity. When users are redirected to malicious sites through open redirect vulnerabilities, they may unknowingly provide credentials or sensitive information to attackers. The cross-site scripting component can lead to session hijacking, data exfiltration, or the delivery of malware to unsuspecting users. These attacks can be particularly dangerous in server environments where legitimate users trust the application's functionality and navigation behavior. The vulnerability affects not just individual web applications but potentially entire server infrastructures that rely on proper URL validation for security.
Organizations should implement comprehensive mitigations including robust input validation, strict URL scheme enforcement, and proper output encoding to prevent malicious URL manipulation. The recommended approach involves using established security libraries and frameworks that handle URL parsing with built-in sanitization capabilities rather than relying on custom implementations. Security teams should also implement monitoring and logging of URL processing activities to detect potential exploitation attempts. According to ATT&CK framework, this vulnerability maps to T1583.002 for Pre-Installation Phase: Software Piracy and potentially T1071.004 for Application Layer Protocol: DNS, highlighting the need for network-level protections alongside application-level fixes. Regular security updates and patch management procedures should be enforced to ensure all systems receive the necessary protections against such vulnerabilities in their respective software versions.