CVE-2016-4721 Apple CVE debrief

Who should care

Anyone running affected Apple devices, especially organizations that rely on caller identity, call routing, or voice-based verification on iOS or macOS. Security teams should prioritize devices that remained on iOS versions before 10.1 or macOS versions before 10.12.1 at the time of exposure.

Technical summary

NVD describes the weakness as a network-reachable issue with high attack complexity and no privileges required, where a man-in-the-middle attacker could influence the IDS - Connectivity path enough to trigger or abuse a "switch caller" notification and spoof a call. The recorded CVSS vector is CVSS:3.0/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:H/A:N, and NVD maps the weakness to CWE-254.

Defensive priority

Medium. The flaw is limited to integrity impact and requires a man-in-the-middle position, but it affects caller identity signaling on widely deployed Apple platforms and was patched in OS updates.

Recommended defensive actions

• Upgrade iOS devices to version 10.1 or later.
• Upgrade macOS systems to version 10.12.1 or later.
• Verify fleet compliance for any devices that may still be on pre-patch Apple operating system versions.
• Review business processes that rely on call identity indicators so they do not depend on unverified caller display alone.
• Use Apple vendor advisories and the NVD record to confirm affected versions and remediation status.

Evidence notes

The description, affected versions, and CVSS vector are taken from the NVD record for CVE-2016-4721. The record lists iOS before 10.1 and macOS before 10.12.1 as vulnerable and cites Apple vendor advisories HT207271 and HT207275. A SecurityFocus BID reference is also present in the source corpus. No unsupported exploit steps or unverified technical details are included.

Official resources