CVE-2020-9860 in Safari
Summary
by MITRE • 10/28/2020
A custom URL scheme handling issue was addressed with improved input validation. This issue is fixed in Safari 13.0.5. Processing a maliciously crafted URL may lead to arbitrary javascript code execution.
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Analysis
by VulDB Data Team • 11/29/2020
The vulnerability identified as CVE-2020-9860 represents a critical security flaw in Apple Safari's handling of custom URL schemes that could potentially enable remote code execution through maliciously crafted web content. This issue specifically affects the browser's input validation mechanisms when processing custom URL schemes, which are protocols that allow web applications to communicate with native applications installed on the user's system. The vulnerability arises from insufficient sanitization of URL parameters that could be exploited by attackers to inject and execute arbitrary JavaScript code within the browser context.
The technical flaw manifests in Safari's improper validation of custom URL scheme handlers, where the browser fails to adequately sanitize user-supplied input before processing it. When a web page attempts to invoke a custom URL scheme through JavaScript methods such as window.location or similar navigation functions, the browser should validate that the provided URL parameters do not contain malicious content that could be interpreted as executable code. However, the vulnerability allows attackers to craft URLs that bypass these validation checks, enabling the execution of arbitrary JavaScript code within the context of the targeted web page or application.
This vulnerability operates under the broader category of input validation flaws that align with CWE-20, which describes "Improper Input Validation" as a fundamental weakness in software design that occurs when applications fail to properly validate or sanitize input data. The attack vector typically involves social engineering techniques where users are诱导 to click on malicious links or visit compromised websites that contain the crafted URLs. The operational impact extends beyond simple code execution as this vulnerability could potentially enable more sophisticated attacks including session hijacking, data exfiltration, or privilege escalation depending on the user's access level and the applications that respond to the custom URL schemes.
The exploitation of CVE-2020-9860 follows patterns consistent with the ATT&CK framework's technique T1059.007 for "Command and Scripting Interpreter: JavaScript" where attackers leverage browser-based scripting languages to execute malicious code. The vulnerability's remediation through Safari 13.0.5 demonstrates Apple's recognition of the severity of the issue, implementing improved input validation mechanisms to prevent malicious URL parameters from being processed as executable code. Security practitioners should note that this vulnerability represents a classic example of how browser-based input validation failures can create attack surfaces that enable arbitrary code execution, making it particularly dangerous in enterprise environments where users may have elevated privileges.
Organizations should prioritize updating Safari browsers to version 13.0.5 or later to mitigate this vulnerability, while security teams should monitor for potential exploitation attempts through web-based attack vectors. The fix addresses the root cause by implementing stricter validation of URL parameters before they are processed by the browser's custom URL scheme handler, preventing malicious input from being interpreted as executable code. Additionally, network security controls such as web application firewalls and content filtering solutions should be configured to detect and block suspicious URL patterns that might attempt to exploit similar vulnerabilities in other browsers or applications.