CVE-2016-4763 in iOS
Summary
by MITRE
WKWebView in WebKit in Apple iOS before 10, iTunes before 12.5.1 on Windows, and Safari before 10 does not properly verify X.509 certificates from HTTPS servers, which allows man-in-the-middle attackers to spoof servers and obtain sensitive information via a crafted certificate.
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Analysis
by VulDB Data Team • 09/20/2022
The vulnerability identified as CVE-2016-4763 represents a critical certificate validation flaw within Apple's WebKit implementation that affected multiple platforms including iOS versions prior to 10, iTunes on Windows versions before 12.5.1, and Safari versions before 10. This weakness stems from inadequate X.509 certificate verification mechanisms that permit malicious actors to execute successful man-in-the-middle attacks by presenting forged certificates that appear legitimate to affected applications. The flaw operates at the core of secure communication protocols where certificate validation should establish trust between client and server, creating a significant security gap that undermines the fundamental purpose of HTTPS encryption.
The technical nature of this vulnerability lies in the improper handling of certificate chain validation within WKWebView components, which are responsible for rendering web content in Apple's mobile and desktop applications. When applications attempt to establish secure connections to HTTPS servers, the flawed verification process fails to properly validate certificate signatures, issuer information, and trust chains that should confirm the authenticity of server certificates. This allows attackers to generate certificates that pass the validation checks despite being untrusted or malicious, effectively breaking the cryptographic trust model that HTTPS relies upon. The vulnerability specifically impacts the certificate verification logic within the WebKit framework, making it particularly dangerous as it affects a core component used across multiple Apple applications and platforms.
The operational impact of CVE-2016-4763 is severe and far-reaching given the widespread use of affected Apple products and applications. Attackers exploiting this vulnerability could intercept and modify sensitive data transmitted between users and web servers, potentially accessing personal information, financial data, login credentials, and other confidential communications. The vulnerability particularly affects users of mobile devices running older iOS versions, desktop users of iTunes on Windows, and Safari browser users, creating a broad attack surface that spans both mobile and desktop computing environments. Organizations relying on Apple products for secure communications face significant risk of data breaches and privacy violations, as the flaw enables attackers to impersonate legitimate websites and services without detection.
Mitigation strategies for this vulnerability require immediate patching of affected systems to upgrade to supported versions of iOS, iTunes, and Safari that contain corrected certificate validation logic. Apple released updates addressing this issue in iOS 10, iTunes 12.5.1, and Safari 10, which implement proper X.509 certificate verification mechanisms that align with industry standards for secure communication. Security administrators should prioritize deployment of these updates across all affected devices and applications, particularly in enterprise environments where sensitive data transmission occurs regularly. Additional defensive measures include implementing network monitoring to detect unusual certificate behavior, deploying certificate pinning techniques where applicable, and conducting regular security assessments to identify potential exploitation attempts. The vulnerability demonstrates the critical importance of proper certificate validation in maintaining secure communications and aligns with CWE-295 which addresses improper certificate validation, while also mapping to ATT&CK technique T1041 for data compression and T1566 for credential access through man-in-the-middle attacks. Organizations should also consider implementing additional security controls such as network segmentation, intrusion detection systems, and regular security audits to reduce the attack surface and prevent exploitation of similar vulnerabilities in the future.