CVE-2020-27923 – This vulnerability allows arbitrary code execut... (How to Fix)

Q: What is the severity of CVE-2020-27923?

CVE-2020-27923 has a CVSS score of 7.8 (HIGH). This vulnerability allows arbitrary code execution through malicious image processing. An attacker can craft a malicious image that triggers an out-of-bounds write when processed by affected Apple operating systems, potentially leading to full system compromise. All users running vulnerable versions of macOS, iOS, iPadOS, watchOS, and tvOS are affected.

📋 TL;DR

This vulnerability allows arbitrary code execution through malicious image processing. An attacker can craft a malicious image that triggers an out-of-bounds write when processed by affected Apple operating systems, potentially leading to full system compromise. All users running vulnerable versions of macOS, iOS, iPadOS, watchOS, and tvOS are affected.

💻 Affected Systems

Products:

macOS
iOS
iPadOS
watchOS
tvOS

Versions: Versions prior to macOS Big Sur 11.1, Security Update 2020-001 Catalina, Security Update 2020-007 Mojave, macOS Big Sur 11.0.1, iOS 14.2, iPadOS 14.2, watchOS 7.1, tvOS 14.2

Operating Systems: macOS, iOS, iPadOS, watchOS, tvOS

Default Config Vulnerable: ⚠️ Yes

Notes: All default configurations are vulnerable. Image processing is a core system function.

📦 What is this software?

⚠️ Risk & Real-World Impact

🔴

Worst Case

Complete system compromise with kernel-level privileges, allowing attacker to install persistent malware, steal sensitive data, or pivot to other systems.

🟠

Likely Case

Malicious app or website delivers crafted image that triggers exploit, leading to user-level code execution and potential data theft.

🟢

If Mitigated

With proper patching, no impact. With network segmentation and least privilege, lateral movement limited.

🌐 Internet-Facing: MEDIUM - Requires user interaction (opening malicious image) but can be delivered via websites or email.

🏢 Internal Only: MEDIUM - Internal users could be targeted via phishing or malicious documents containing crafted images.

🎯 Exploit Status

Public PoC: ✅ No

Weaponized: UNKNOWN

Unauthenticated Exploit: ⚠️ Yes

Complexity: MEDIUM

Exploitation requires user to process malicious image but no authentication needed. Apple has patched this vulnerability.

🛠️ Fix & Mitigation

✅ Official Fix

Patch Version: macOS Big Sur 11.1, Security Update 2020-001 Catalina, Security Update 2020-007 Mojave, macOS Big Sur 11.0.1, iOS 14.2, iPadOS 14.2, watchOS 7.1, tvOS 14.2

Vendor Advisory: https://support.apple.com/en-us/HT211928

Restart Required: Yes

Instructions:

1. Open System Preferences > Software Update. 2. Install all available updates. 3. Restart when prompted. For iOS/iPadOS: Settings > General > Software Update. For watchOS: iPhone Watch app > General > Software Update. For tvOS: Settings > System > Software Updates.

🔧 Temporary Workarounds

Image Processing Restriction

all

Restrict processing of untrusted image files through application controls or policies.

🧯 If You Can't Patch

Implement network segmentation to isolate vulnerable systems
Apply strict application whitelisting to prevent unknown image processing applications

🔍 How to Verify

Check if Vulnerable:

Check current OS version against patched versions listed in Apple advisories.

Check Version:

macOS: sw_vers; iOS/iPadOS: Settings > General > About; watchOS: iPhone Watch app > General > About; tvOS: Settings > General > About

Verify Fix Applied:

Verify OS version matches or exceeds patched versions: macOS: About This Mac > Overview; iOS/iPadOS: Settings > General > About; watchOS: iPhone Watch app > General > About; tvOS: Settings > General > About.

📡 Detection & Monitoring

Log Indicators:

Unexpected process crashes related to image processing
Memory access violations in system logs
Unusual image file processing from untrusted sources

Network Indicators:

Downloads of suspicious image files from unknown sources
Outbound connections from image processing applications to unknown IPs

SIEM Query:

source="apple_system_logs" AND (process="image" OR process="graphics") AND (event="crash" OR event="access_violation")

📊 Metadata

CVE ID: CVE-2020-27923

CVSS v3 Score: 7.8 (HIGH)

CVSS Vector: CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H

CWE: CWE-787

Published: April 2, 2021

Last Updated: November 21, 2024

🔗 References

https://support.apple.com/en-us/HT211928 Vendor Advisory
https://support.apple.com/en-us/HT211929 Vendor Advisory
https://support.apple.com/en-us/HT211930 Vendor Advisory
https://support.apple.com/en-us/HT211931 Vendor Advisory
https://support.apple.com/en-us/HT212011 Vendor Advisory
https://support.apple.com/en-us/HT211928 Vendor Advisory
https://support.apple.com/en-us/HT211929 Vendor Advisory
https://support.apple.com/en-us/HT211930 Vendor Advisory
https://support.apple.com/en-us/HT211931 Vendor Advisory
https://support.apple.com/en-us/HT212011 Vendor Advisory

📤 Share & Export

📄 Export Markdown 📋 Export JSON

🔗 Related Vulnerabilities

If you're affected by CVE-2020-27923, you might also want to check these: