Font Parser Vulnerability in Apple Products Allows Process Crashes and Memory Corruption

Apple releases security update for macOS Sequoia 15.7.1 addressing CVE-2025-43400, a font parser vulnerability that could crash applications or corrupt memory through malicious fonts.

Apple has issued an urgent security update for macOS Sequoia to address a significant vulnerability in its font parsing system that could allow attackers to crash applications or corrupt process memory using specially crafted font files.

Critical Font Parser Flaw Addressed

The vulnerability, designated as CVE-2025-43400, represents a serious security flaw in Apple’s font parser that enables malicious font files to trigger out-of-bounds write operations.

This type of memory corruption vulnerability poses substantial risks as it could lead to unexpected application termination or, more concerning, corrupt process memory in ways that might be exploited for further attacks.

Apple released the fix on September 29, 2025, as part of the macOS Sequoia 15.7.1 security update.

The company’s security advisory emphasizes the critical nature of this vulnerability, though no active exploitation has been reported in the wild at this time.

The font parser vulnerability affects multiple Apple platforms beyond macOS, demonstrating the interconnected nature of Apple’s operating system components.

The security fix has been deployed across iOS 26.0.1, iPadOS 26.0.1, iOS 18.7.1, iPadOS 18.7.1, macOS Tahoe 26.0.1, macOS Sequoia 15.7.1, macOS Sonoma 14.8.1, and visionOS 26.0.1.

This broad platform coverage indicates that the vulnerable font parsing code is shared across Apple’s ecosystem, making the coordinated patch release particularly important for maintaining security consistency across devices.

CVE Details and Technical Analysis

The vulnerability’s exploitation mechanism requires attackers to deliver maliciously crafted font files to target systems.

While this might seem like a limited attack vector, fonts are commonly embedded in documents, websites, and applications, making it potentially easier for attackers to distribute malicious payloads.

Security researchers note that memory corruption vulnerabilities like CVE-2025-43400 often serve as building blocks for more sophisticated attacks.

While the immediate impact involves application crashes and memory corruption, skilled attackers could potentially chain this vulnerability with other exploits to achieve remote code execution.

The out-of-bounds write capability means attackers could potentially overwrite critical memory structures, leading to privilege escalation or arbitrary code execution under certain conditions.

This makes the vulnerability particularly concerning for enterprise environments where font files might be processed automatically.

Apple users should prioritize installing the security update immediately.

Systems configured for automatic updates will receive the patch during their next update cycle, while users with manual update settings should navigate to System Settings > General > Software Update to download macOS Sequoia 15.7.1.

Organizations managing Apple device fleets should verify their update policies to ensure comprehensive coverage across all affected platforms, including mobile devices and mixed-OS environments.

The coordinated nature of this security release across multiple Apple platforms underscores the importance of maintaining consistent patch management practices.

This vulnerability highlights the ongoing security challenges posed by font parsing systems and reinforces the critical importance of treating font files from untrusted sources with appropriate caution.

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