CVE-2025-43494 is a security vulnerability identified in Apple macOS and other Apple operating systems related to mail header parsing. The vulnerability arises from insufficient validation or improper handling of mail headers, which an attacker can exploit by crafting malicious mail headers that trigger a persistent denial-of-service condition. This DoS is persistent, meaning the affected system may remain inoperable or unstable until a manual recovery or patch is applied, potentially requiring a system reboot or more extensive remediation. The issue affects multiple Apple OS versions, including macOS Tahoe 26.1, macOS Sonoma 14.8.2, macOS Sequoia 15.7.2, iOS 18.7.2 and 26.1, iPadOS 18.7.2 and 26.1, watchOS 26.1, and visionOS 26.1. Apple has addressed the vulnerability by implementing improved checks in mail header parsing routines. The vulnerability was reserved in April 2025 and published in December 2025, with no CVSS score assigned yet and no known exploits in the wild. Exploitation likely requires sending a specially crafted mail header to the target device, which may not require user interaction or authentication, increasing the risk profile. The vulnerability impacts confidentiality minimally but significantly affects availability due to the persistent DoS. The scope includes all affected Apple devices running vulnerable OS versions, which are widely used in enterprise and consumer environments.

For European organizations, the primary impact of CVE-2025-43494 is the potential for persistent denial-of-service on Apple devices, which can disrupt business operations, especially in environments that rely on Apple hardware and software for communication and productivity. Persistent DoS could lead to prolonged downtime of critical systems, affecting mail services, endpoint availability, and user productivity. Organizations in sectors such as finance, healthcare, government, and technology that use Apple ecosystems extensively may face operational disruptions. The persistence of the DoS means recovery may require manual intervention or reimaging, increasing incident response costs and downtime. Additionally, the lack of known exploits currently provides a window for proactive patching, but the ease of exploitation via mail headers means attackers could weaponize this quickly once public details are widely known. The impact on confidentiality and integrity is low, but availability impact is high, which can indirectly affect business continuity and trust.

To mitigate CVE-2025-43494, European organizations should prioritize deploying the security updates released by Apple for all affected operating systems, including macOS Sonoma 14.8.2, macOS Sequoia 15.7.2, iOS 26.1, iPadOS 26.1, watchOS 26.1, and visionOS 26.1. Organizations should implement strict mail filtering and validation at the mail gateway to detect and block malformed or suspicious mail headers that could exploit this vulnerability. Monitoring mail server logs for unusual header patterns or repeated failures can help detect attempted exploitation. Endpoint detection and response (EDR) tools should be configured to alert on abnormal application crashes or system instability related to mail clients. Network segmentation can limit the spread or impact of a successful DoS attack. User awareness campaigns should inform users about suspicious emails, although user interaction may not be required for exploitation. Incident response plans should include procedures for recovery from persistent DoS conditions, including system reboots and patch verification. Regular vulnerability scanning and asset inventory to identify all Apple devices running vulnerable OS versions are essential for comprehensive mitigation.