Apple iOS, macOS, watchOS FontParser Memory Corruption Remote Code Execution Vulnerability (CVE-2020-27930)
Executive & SecOps Summary
SECOPS ASSESSMENTLegacy Apple operating systems prior to iOS 14.2, macOS Catalina 10.15.7, and watchOS 7.1
Processing a maliciously crafted font file triggers an out-of-bounds write (CWE-787), leading to arbitrary remote code execution (RCE)
Immediately apply the official security patches provided by Apple (iOS 14.2, macOS Big Sur 11.0.1, or later)
Affected Products & Version Scope
Remediation & Live Workaround Commands
PATCH & WORKAROUND1. Official Patch & Version Upgrade Commands
Apply the official security updates provided by Apple immediately to resolve the vulnerability.
On macOS, you can force the system to check and install updates via the terminal:
# List available software updates
softwareupdate -l
# Download and install all available security updates and restart if required
sudo softwareupdate -iaR2. Temporary Workaround & Hardening Configuration
If immediate patching is not feasible, restrict access to untrusted websites and temporarily use alternative browsers with robust sandboxing. For enterprise environments, deploy MDM profiles to restrict the installation of untrusted configuration profiles and custom fonts.
# Example command to verify installed configuration profiles via CLI
profiles -L3. Log Audit & IoC Verification Commands
Check the current macOS system version and inspect system logs for any abnormal FontParser crashes:
# Check macOS system version and build number
sw_vers
# Query system logs for FontParser-related crashes or exceptions
log show --predicate 'process == "FontParser"' --info | grep -E -i 'crash|exception|corrupt'Block Kernel Privilege Escalation & Ransomware Payloads Before You Can Reboot
Protect unpatched Windows, Linux, and macOS workloads against in-memory exploitation and lateral movement with autonomous EDR.
Technical Root Cause & Exploitation Mechanics
1. Vulnerability Overview & Root Cause
This vulnerability (CVE-2020-27930) is a critical memory corruption issue residing within the FontParser library, a core component of Apple operating systems responsible for parsing font files. Due to insufficient input validation when processing font metadata and glyph data, an out-of-bounds write (CWE-787) can be triggered. This corruption of heap or stack memory allows attackers to hijack the application's control flow.
2. Exploitation Mechanics & Attack Scenario
An attacker exploits this vulnerability by crafting a malicious font file (such as TrueType or OpenType) and embedding it within a web page, an email attachment, or a document. When a victim visits a compromised website via Safari or opens an application that renders the malicious font, the FontParser is triggered. This requires minimal user interaction (UI) and allows the execution of arbitrary shellcode within the context of the rendering process.
3. Infrastructure & Business Impact
This vulnerability is actively exploited in the wild and is listed in the CISA KEV (Known Exploited Vulnerabilities) catalog. Attackers frequently chain this RCE with local privilege escalation (LPE) vulnerabilities (such as CVE-2020-27950 and CVE-2020-27932) to compromise the kernel and gain full control of the device. In an enterprise environment, this poses a severe threat as a single web-browsing session on an unpatched MacBook or iPhone could lead to initial access and lateral movement within the corporate network.
Official Vendor Advisories & References
A memory corruption issue was addressed with improved input validation. This issue is fixed in macOS Big Sur 11.0.1, watchOS 7.1, iOS 12.4.9, watchOS 6.2.9, Security Update 2020-006 High Sierra, Security Update 2020-006 Mojave, iOS 14.2 and iPadOS 14.2, watchOS 5.3.9, macOS Catalina 10.15.7 Supplemental Update, macOS Catalina 10.15.7 Update. Processing a maliciously crafted font may lead to arbitrary code execution.
Frequently Asked SecOps Questions (CVE-2020-27930)
FAQQ1. How critical is CVE-2020-27930 and is it actively exploited in the wild?
CVE-2020-27930 is rated CVSS 7.8 (HIGH) with a 30-day EPSS exploitation probability of 22.0%. It is listed in the CISA Known Exploited Vulnerabilities (KEV) catalog, requiring immediate emergency remediation.
Q2. Which vendors and products are affected by CVE-2020-27930?
Primary impacted vendors include apple across macos, ios, ipados, watchos, safari. Scope summary: Systems running versions prior to iOS 14.2, iPadOS 14.2, macOS Catalina 10.15.7, watchOS 7.1, watchOS 6.2.9, watchOS 5.3.9, and iOS 12.4.9
Q3. What temporary mitigations or workarounds exist for CVE-2020-27930 before patching?
[Mitigation] Immediately apply the official security patches provided by Apple (iOS 14.2, macOS Big Sur 11.0.1, or later) Follow the CLI remediation commands and interactive SecOps checklist on this page to restrict exposure prior to your maintenance window.
Generate an Internal Engineering Notice or CISO Report for CVE-2020-27930
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