CVE-2016-2567 in Note 3
Summary
by MITRE
secfilter in the Samsung kernel for Android on SM-N9005 build N9005XXUGBOB6 (Note 3) and SM-G920F build G920FXXU2COH2 (Galaxy S6) devices allows attackers to bypass URL filtering by inserting an "exceptional URL" in the query string, as demonstrated by the http://should-have-been-filtered.example.com/?http://google.com URL.
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Analysis
by VulDB Data Team • 08/30/2020
The vulnerability identified as CVE-2016-2567 represents a critical flaw in the Samsung kernel's security filtering mechanism affecting specific Android devices including the Galaxy Note 3 SM-N9005 and Galaxy S6 SM-G920F. This weakness resides within the secfilter component that is responsible for enforcing URL filtering policies to prevent access to malicious or restricted web content. The vulnerability demonstrates a sophisticated bypass technique that exploits the kernel's handling of query strings in web addresses, allowing attackers to circumvent security controls that should have blocked access to filtered domains. The attack vector is particularly concerning because it leverages the legitimate parsing of URL parameters to create a scenario where a secondary URL embedded within the query string is not properly evaluated against security policies. The specific demonstration shows how a URL formatted as http://should-have-been-filtered.example.com/?http://google.com could potentially bypass filtering mechanisms, where the embedded http://google.com portion in the query string is not subject to the same security checks as the primary domain.
The technical implementation of this vulnerability stems from improper input validation within the kernel's URL parsing logic, where the secfilter component fails to adequately sanitize or process query string parameters that contain additional URLs. This represents a classic case of insufficient input sanitization and improper URL handling, which aligns with CWE-20 - Improper Input Validation and CWE-77 - Command Injection patterns. The flaw occurs at the kernel level in Android's security framework, where the filtering logic does not properly distinguish between the primary URL being accessed and secondary URLs embedded within query parameters. This creates a condition where the security system's evaluation process is bypassed for the embedded URL, allowing unauthorized access to content that should have been blocked. The vulnerability specifically affects the Samsung kernel implementation and demonstrates how device-specific security measures can contain implementation flaws that undermine the overall security posture.
The operational impact of this vulnerability extends beyond simple access bypass to potentially enable more sophisticated attacks including phishing, malware delivery, and unauthorized access to restricted content. Attackers could exploit this flaw to redirect users to malicious sites while appearing to originate from legitimate domains, making detection and prevention significantly more difficult. The vulnerability affects devices running specific firmware versions where the kernel's security filtering has not been properly updated to address this parsing inconsistency. Organizations and users with affected devices face increased risk of exposure to malicious web content, particularly in enterprise environments where strict URL filtering policies are implemented. The impact is particularly severe for mobile devices where users may not be aware of the security implications of visiting seemingly benign websites that could contain embedded malicious URLs.
Mitigation strategies for CVE-2016-2567 should focus on both immediate device-level fixes and broader security policy implementations. Samsung released firmware updates to address this vulnerability, and users should immediately install available security patches for their affected devices. Network administrators should implement additional monitoring and filtering measures at the network level to detect and block suspicious URL patterns that may exploit this vulnerability. The solution involves updating kernel components and ensuring proper URL sanitization mechanisms are in place to prevent query string parameter parsing from bypassing security controls. Organizations should also consider implementing additional security controls such as web application firewalls, proxy-based filtering, and enhanced monitoring of web traffic patterns that could indicate exploitation attempts. This vulnerability highlights the importance of thorough security testing for kernel-level components and the need for comprehensive input validation across all system layers. The ATT&CK framework categorizes this as a technique involving command and control through web-based protocols, where the vulnerability enables attackers to establish persistent access through manipulated URL structures that bypass standard security controls.