CVE-2020-3837 Overview
CVE-2020-3837 is a memory corruption vulnerability affecting the kernel across multiple Apple operating systems. An application can exploit the flaw to execute arbitrary code with kernel privileges. The issue impacts iOS, iPadOS, macOS Catalina, tvOS, and watchOS, and was resolved through improved memory handling in Apple's January 2020 security updates.
The vulnerability is tracked under [CWE-787] (Out-of-Bounds Write) and is listed in the CISA Known Exploited Vulnerabilities catalog, indicating confirmed exploitation in the wild. Local attack access with user interaction is required, but successful exploitation yields full kernel-level compromise of the affected device.
Critical Impact
A malicious application running locally can corrupt kernel memory and execute arbitrary code with kernel privileges, fully compromising the device.
Affected Products
- Apple iOS and iPadOS (versions prior to 13.3.1)
- Apple macOS Catalina (versions prior to 10.15.3)
- Apple tvOS (prior to 13.3.1) and watchOS (prior to 6.1.2)
Discovery Timeline
- 2020-02-27 - CVE-2020-3837 published to NVD
- 2025-10-23 - Last updated in NVD database
Technical Details for CVE-2020-3837
Vulnerability Analysis
The flaw resides in the kernel component shared across Apple's operating systems. Apple's advisories describe the issue as a memory corruption condition resolved with improved memory handling. The underlying weakness is classified as [CWE-787], an out-of-bounds write, where the kernel writes data past the bounds of an allocated buffer.
Successful exploitation allows a local application to corrupt kernel memory structures. Because the corruption occurs inside the kernel address space, the attacker can pivot from an unprivileged process to ring-0 execution. This breaks the sandbox boundaries enforced on iOS, iPadOS, tvOS, and watchOS applications.
The vulnerability is confirmed exploited according to CISA KEV listing, making it relevant for jailbreak chains and targeted mobile implants of the period.
Root Cause
The root cause is improper validation of memory bounds within a kernel routine. When attacker-controlled input reaches the vulnerable code path, the kernel writes outside the intended buffer, overwriting adjacent data structures. Apple addressed this by adding stricter bounds checks and validation logic in the affected kernel paths.
Attack Vector
Exploitation requires local access through a malicious or compromised application. The attacker must convince a user to install or run a crafted application. Once executing, the application issues calls that trigger the out-of-bounds write in the kernel, leveraging the corruption primitive to escalate to kernel privileges.
The vulnerability cannot be triggered remotely without prior code execution on the device. However, it pairs with browser or messaging exploits to form complete remote compromise chains, which is consistent with patterns observed in real-world iOS exploit kits.
No public proof-of-concept code is referenced in the advisories. See Apple Support Document HT210918 for vendor technical details.
Detection Methods for CVE-2020-3837
Indicators of Compromise
- Unexpected kernel panics or crash reports referencing memory corruption in panic-full.log or CrashReporter artifacts on iOS and macOS devices.
- Installation of unsigned or sideloaded applications that request unusual entitlements prior to crash events.
- Devices running iOS, iPadOS, tvOS, or watchOS firmware versions below the patched releases (13.3.1, 10.15.3, 6.1.2).
Detection Strategies
- Inventory all Apple endpoints and flag devices running operating system versions earlier than iOS/iPadOS 13.3.1, macOS Catalina 10.15.3, tvOS 13.3.1, or watchOS 6.1.2.
- Review Mobile Device Management (MDM) compliance reports for outdated OS builds and enforce patch baselines.
- Correlate application installation telemetry with kernel crash reports to identify suspicious applications triggering instability.
Monitoring Recommendations
- Forward iOS and macOS crash logs to a centralized logging platform for kernel panic analysis.
- Monitor MDM enrollment and patch-state telemetry continuously, alerting when devices fall behind on security updates.
- Track CISA KEV catalog updates and align internal vulnerability management SLAs to KEV remediation deadlines.
How to Mitigate CVE-2020-3837
Immediate Actions Required
- Update affected devices to iOS 13.3.1, iPadOS 13.3.1, macOS Catalina 10.15.3, tvOS 13.3.1, or watchOS 6.1.2 or later.
- Audit installed applications and remove unsigned, sideloaded, or untrusted software from managed devices.
- Enforce MDM policies that block enrollment of devices running unpatched operating system versions.
Patch Information
Apple released fixes through the following security updates: Apple Support Document HT210918, HT210919, HT210920, and HT210921. The patches introduce improved memory handling in the kernel code path. Devices receive the update through the standard Software Update mechanism in Settings or System Preferences.
Workarounds
- No vendor-provided workaround exists; patching is the only supported remediation.
- Restrict application installation to the official App Store and approved enterprise distribution channels until devices are updated.
- Enable automatic updates on all managed Apple devices to reduce exposure windows for future kernel vulnerabilities.
# Configuration example: verify patched OS version on macOS
sw_vers -productVersion
# Expected output: 10.15.3 or later for Catalina systems
# On iOS/iPadOS via MDM query, ensure ProductVersion >= 13.3.1
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
