CVE-2015-1129 in iOS
Summary
by MITRE
Apple Safari before 6.2.5, 7.x before 7.1.5, and 8.x before 8.0.5 does not properly select X.509 client certificates, which makes it easier for remote attackers to track users via a crafted web site.
Be aware that VulDB is the high quality source for vulnerability data.
Analysis
by VulDB Data Team • 06/16/2022
This vulnerability in Apple Safari browsers represents a significant privacy and security concern related to X.509 certificate handling during TLS client authentication. The flaw exists in versions prior to 6.2.5, 7.1.5, and 8.0.5 respectively, where the browser fails to properly select client certificates when multiple certificates are available. This improper certificate selection mechanism creates a predictable pattern that can be exploited by malicious websites to track user activities across different sessions and connections.
The technical implementation issue stems from Safari's certificate selection algorithm not adequately randomizing or varying the certificate choice when multiple valid client certificates exist in the user's keychain. This behavior creates a consistent fingerprint that attackers can observe and correlate across different web interactions, effectively enabling persistent tracking mechanisms. The vulnerability falls under CWE-295 which addresses improper certificate validation and certificate selection issues in cryptographic implementations. When a website presents multiple certificate options during TLS handshake, the browser's failure to properly randomize or select certificates based on appropriate security criteria allows for tracking through certificate reuse patterns.
From an operational perspective, this vulnerability enables sophisticated tracking attacks where malicious websites can monitor user behavior across different sessions and connections. The tracking mechanism works by observing which certificate is selected by the browser during various interactions, creating a persistent identifier that can be used to correlate user activities. This represents a significant privacy violation as it undermines the expected anonymity of web browsing sessions. The attack vector is particularly concerning because it operates at the TLS layer, making it difficult for traditional network monitoring tools to detect the tracking activity.
The implications extend beyond simple tracking to potential identity correlation across different services and websites. Attackers can leverage this flaw to build comprehensive user profiles by observing certificate selection patterns over time, creating persistent identifiers that bypass typical privacy protections. This vulnerability aligns with ATT&CK technique T1566 which covers credential access through phishing and social engineering, as it enables more sophisticated tracking that can be used in conjunction with other attack vectors. The flaw essentially provides attackers with a persistent tracking mechanism that operates below the user's awareness, making it particularly dangerous for privacy-conscious users and organizations requiring secure browsing environments.
Organizations should immediately update Safari browsers to the patched versions to remediate this vulnerability. The mitigation strategy involves ensuring all users have the latest Safari updates installed, which properly implement certificate selection algorithms that randomize or appropriately choose certificates during TLS handshakes. System administrators should also consider implementing network monitoring to detect anomalous certificate selection patterns that might indicate exploitation attempts. Additionally, users should be educated about the importance of keeping their browsers updated and the potential privacy implications of certificate-based tracking mechanisms in web browsers.