CVE-2020-3837

What Makes Kernel-Level Bugs on Apple Devices Different?

Apple's app sandboxing model relies on strict isolation between an app and the kernel — a compromised or malicious app should only affect its own data. A kernel-level memory corruption bug breaks that isolation, letting an app escalate from its sandboxed context to full kernel privileges, which is why bugs like this one are the essential second half of complete jailbreak and targeted-exploitation chains.

Overview

CVE-2020-3837 is a memory corruption vulnerability (CWE-787) affecting iOS, iPadOS, macOS, tvOS, and watchOS that could allow a malicious application to execute code with kernel privileges (CVSS 3.1: AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H, 7.8 High), fixed across all five OS families in March 2020.

Technical Details

The vulnerability allows an application, once it has some form of initial code execution, to trigger memory corruption in the kernel that an attacker can shape to escalate privileges beyond the app sandbox's normal restrictions — the same general privilege-escalation pattern documented in several other Apple kernel bugs on this site, such as CVE-2020-9859 and CVE-2020-27932.

Discovery

Fixed as part of Apple's routine iOS 13.4 / iPadOS 13.4 release cycle and corresponding macOS, tvOS, and watchOS updates.

Exploitation Context

CISA added this CVE to KEV in June 2022 based on confirmed exploitation. As with most Apple kernel bugs, this vulnerability is most valuable to an attacker as the privilege-escalation component of a broader exploitation chain rather than as a standalone initial-access vector.

Remediation

1. Update every affected Apple OS — iOS, iPadOS, macOS, tvOS, and watchOS — to the version including this fix or later.
2. Enable automatic software updates across managed Apple device fleets.
3. Deploy mobile threat detection tooling for high-risk users who may be targeted with sophisticated multi-stage exploitation chains.
4. Confirm all affected platforms are patched, not just the primary one you manage — this bug spans five distinct Apple OS families simultaneously.