CVE-2020-3843: Apple iPhone OS Buffer Overflow Vulnerability

CVE-2020-3843 Overview

CVE-2020-3843 is a memory corruption vulnerability affecting Apple iOS and watchOS. The flaw stems from improper input validation in kernel-level code processing wireless radio proximity data. A remote attacker within radio range can trigger unexpected system termination or corrupt kernel memory on vulnerable devices.

Apple addressed the issue in iOS 12.4.7 and watchOS 5.3.7 through improved input validation. The vulnerability is classified under [CWE-787] (Out-of-bounds Write) and requires user interaction for exploitation. Public exploit analysis exists via Packet Storm, demonstrating radio-proximity-based kernel memory corruption against iOS and macOS devices.

Critical Impact

A remote attacker within wireless range can corrupt kernel memory, causing system termination or potentially achieving arbitrary code execution at the kernel level on affected Apple devices.

Affected Products

• Apple iOS prior to version 12.4.7
• Apple watchOS prior to version 5.3.7
• Apple iPhone and Apple Watch devices running vulnerable firmware

Discovery Timeline

• 2020-02-27 - CVE-2020-3843 published to NVD
• 2024-11-21 - Last updated in NVD database

Technical Details for CVE-2020-3843

Vulnerability Analysis

The vulnerability resides in kernel code handling wireless radio proximity data. Improper input validation allows attacker-controlled data to trigger an out-of-bounds memory write condition [CWE-787]. The flaw enables a remote attacker to corrupt kernel memory structures or terminate the affected device unexpectedly.

Exploitation does not require authentication but requires user interaction within wireless range of the target device. Successful exploitation impacts confidentiality, integrity, and availability at the kernel level. Published exploit analysis on Packet Storm documents the radio-proximity attack surface used to reach the vulnerable code path.

Root Cause

The root cause is missing or insufficient bounds checking on wireless radio proximity input data processed by the iOS and watchOS kernel. Attacker-supplied data lengths or field values bypass validation, causing the kernel to write beyond allocated buffer boundaries. This memory corruption condition aligns with the [CWE-787] weakness class.

Attack Vector

The attack vector is network-adjacent through wireless radio protocols. An attacker within proximity of the target device transmits crafted radio frames containing malformed proximity data. When the vulnerable kernel code processes these frames, the malformed input triggers memory corruption. The attack requires the target user to have wireless interfaces enabled and within receive range.

The vulnerability mechanism is described in the Packet Storm exploit analysis. No verified proof-of-concept code is reproduced here; refer to the referenced advisory for technical exploitation details.

Detection Methods for CVE-2020-3843

Indicators of Compromise

• Unexpected kernel panics or device reboots on iOS or watchOS devices in proximity to unknown wireless transmitters
• Anomalous wireless radio activity logs indicating malformed proximity frames
• Crash reports referencing kernel memory corruption in radio or proximity-related subsystems

Detection Strategies

• Monitor iOS and watchOS device crash logs for kernel panics correlated with wireless activity
• Inspect MDM-collected telemetry for devices running iOS versions earlier than 12.4.7 or watchOS earlier than 5.3.7
• Identify devices reporting unexpected restarts in locations with untrusted wireless environments

Monitoring Recommendations

• Enforce minimum OS version compliance through Mobile Device Management policies
• Aggregate device crash reports and correlate with location and wireless context
• Track Apple security advisories HT211169 and HT211176 for related kernel issues

How to Mitigate CVE-2020-3843

Immediate Actions Required

• Update all affected iPhone devices to iOS 12.4.7 or later immediately
• Update all affected Apple Watch devices to watchOS 5.3.7 or later immediately
• Audit enterprise fleet inventories through MDM platforms to identify non-compliant devices
• Restrict use of vulnerable devices in untrusted wireless environments until patched

Patch Information

Apple released fixes in iOS 12.4.7 and watchOS 5.3.7. Patch details are documented in Apple Security Advisory HT211169 and Apple Security Advisory HT211176. The fix improves input validation in the affected kernel code paths.

Workarounds

• Disable wireless radio interfaces when operating in untrusted physical environments
• Limit device exposure to unknown wireless transmitters by enabling airplane mode in high-risk locations
• Apply Mobile Device Management policies enforcing patched OS versions before granting corporate resource access

# Configuration example: MDM compliance query for vulnerable iOS versions
# Pseudocode - adapt to your MDM platform
query: device.os == "iOS" AND device.os_version < "12.4.7"
action: quarantine AND notify_user("Update required for CVE-2020-3843")