CVE-2025-43400 is an out-of-bounds write vulnerability categorized under CWE-787 affecting Apple’s font processing components across multiple operating systems including iOS, iPadOS, macOS, tvOS, visionOS, and watchOS. The vulnerability arises when the system processes a maliciously crafted font file, which triggers improper bounds checking leading to memory corruption. This can result in unexpected application crashes or corruption of process memory, potentially enabling attackers to cause denial of service or, in some scenarios, execute arbitrary code. The vulnerability does not require any privileges to exploit but does require user interaction, such as opening or rendering a malicious font embedded in a document or web content. Apple has released patches in versions iOS 18.7.1, iPadOS 18.7.1, macOS Sequoia 15.7.1, macOS Sonoma 14.8.1, macOS Tahoe 26.0.1, tvOS 26.1, visionOS 26.0.1, and watchOS 26.1 to address this issue by implementing improved bounds checking to prevent out-of-bounds memory writes. No public exploits or active exploitation campaigns have been reported to date, but the vulnerability’s nature and medium CVSS score of 6.3 indicate a moderate risk if left unpatched.

The primary impact of CVE-2025-43400 is on the availability and integrity of affected Apple devices. Exploitation can cause applications to crash unexpectedly, leading to denial of service conditions that disrupt user productivity and critical operations. Memory corruption could also be leveraged by skilled attackers to escalate the attack, potentially executing arbitrary code or bypassing security controls, although this is less certain given the medium severity rating. Organizations relying heavily on Apple ecosystems, especially in sectors where device stability and data integrity are critical (e.g., healthcare, finance, government), could face operational disruptions or targeted attacks exploiting this vulnerability. The requirement for user interaction limits automated exploitation but does not eliminate risk, especially in environments where users frequently open documents or web content from untrusted sources. Failure to patch could expose organizations to increased risk of malware delivery or system compromise via crafted font files embedded in emails, websites, or applications.

To mitigate CVE-2025-43400, organizations should promptly deploy the security updates released by Apple for all affected platforms: iOS 18.7.1, iPadOS 18.7.1, macOS Sequoia 15.7.1, macOS Sonoma 14.8.1, macOS Tahoe 26.0.1, tvOS 26.1, visionOS 26.0.1, and watchOS 26.1. Beyond patching, organizations should implement strict controls on font file sources by restricting or scanning font files embedded in documents and emails, especially those originating from untrusted or external sources. Employing endpoint protection solutions capable of detecting anomalous font processing behavior can provide additional defense. User education to avoid opening suspicious documents or links containing fonts from unknown origins is critical. Network-level protections such as web filtering and email gateway scanning should be configured to block or quarantine potentially malicious font files. Monitoring system logs for application crashes related to font rendering can help detect exploitation attempts. Finally, organizations should maintain up-to-date backups and incident response plans to quickly recover from potential denial of service or compromise scenarios.