CVE-2016-4747

Vulnerability

The Mail application in Apple iOS versions prior to 10 mishandles certificate validation, allowing a man-in-the-middle attacker to potentially discover mail credentials [1]. The vulnerability exists in the certificate handling routines of the operating system. Affected versions include all iOS releases before 10, on iPhone 5 and later, iPad 4th generation and later, and iPod touch 6th generation and later.

Exploitation

An attacker must be in a position to perform a man-in-the-middle attack on the network traffic between the iOS device and the mail server. By presenting a crafted or improperly validated certificate, the attacker can intercept or modify the encrypted communication. The exact vector is not publicly disclosed, but the weakness lies in how iOS versions before 10 handle certificate trust [1]. No authentication, special privileges, or user interaction beyond normal mail usage is required.

Impact

Successful exploitation allows a man-in-the-middle attacker to discover mail credentials, such as usernames and passwords, transmitted by the Mail app. This leads to information disclosure of sensitive authentication data. The compromise is limited to credentials captured over the network and does not grant direct device access or elevated privileges.

Mitigation

The vulnerability is fixed in iOS 10, released on September 13, 2016 [1]. Users should update their devices to iOS 10 or later. No workarounds are available from Apple; disabling automatic mail account configuration or using a VPN may reduce exposure but is not a complete mitigation. This issue is not listed on the CISA Known Exploited Vulnerabilities (KEV) catalog as of this writing.