CVE-2025-43494 is a vulnerability identified in Apple’s mail header parsing logic affecting multiple Apple operating systems including macOS (Sonoma 14.8.2, Tahoe 26.1, Sequoia 15.7.2), iOS, iPadOS, watchOS, and visionOS. The root cause is improper input validation (CWE-20) when parsing mail headers, which can be exploited by an unauthenticated remote attacker sending specially crafted mail data to trigger a persistent denial-of-service condition. This DoS can cause affected systems to become unresponsive or require a reboot, impacting availability. The vulnerability does not affect confidentiality or integrity, and no user interaction is required to exploit it, increasing its risk profile. The CVSS v3.1 base score is 7.5 (AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H), indicating high severity due to network attack vector, low attack complexity, no privileges or user interaction needed, and high impact on availability. Apple released patches in December 2025 across all affected platforms to address the issue by implementing improved validation checks in mail header parsing. There are no known exploits in the wild at the time of publication, but the vulnerability’s characteristics make it a candidate for exploitation in the future. The issue is particularly relevant for organizations relying on Apple devices for mail processing or critical operations, as disruption could affect business continuity. The vulnerability was reserved in April 2025 and publicly disclosed in December 2025.

For European organizations, this vulnerability poses a significant risk to availability of Apple devices and systems involved in mail processing or communication. Persistent denial-of-service conditions could disrupt business operations, especially in sectors relying heavily on Apple ecosystems such as creative industries, finance, and government agencies. The lack of required authentication and user interaction means attackers can remotely target vulnerable systems at scale, potentially causing widespread outages. Critical infrastructure entities using macOS or iOS devices for operational technology or communication may face operational interruptions. Additionally, organizations with Bring Your Own Device (BYOD) policies that include Apple devices could see increased exposure. The impact is primarily on system availability, with no direct compromise of data confidentiality or integrity, but service disruption can lead to indirect consequences such as loss of productivity, customer trust, and regulatory compliance challenges under frameworks like GDPR if service outages affect data processing.

European organizations should prioritize immediate deployment of the security updates released by Apple in December 2025 for all affected operating systems including macOS Sonoma, Tahoe, Sequoia, iOS, iPadOS, watchOS, and visionOS. Network-level filtering of suspicious mail traffic can help reduce exposure to crafted mail headers. Implementing mail gateway security solutions that perform deep inspection and validation of mail headers can provide an additional layer of defense. Organizations should monitor system logs and mail processing components for signs of abnormal crashes or service interruptions indicative of attempted exploitation. Where possible, segment Apple devices handling mail processing from critical infrastructure networks to limit potential impact. Conduct regular vulnerability scanning and asset inventory to ensure all Apple devices are identified and patched promptly. Educate IT staff on the nature of this vulnerability and the importance of patch management. Finally, maintain robust incident response plans to quickly address any denial-of-service incidents.