On September 29, 2025, Apple released security updates addressing a vulnerability tracked as CVE-2025-43400 affecting the Font Parser component in multiple Apple operating systems, including iOS 18 and 26, macOS versions back to Sonoma (14), and visionOS 26. The vulnerability arises from the improper handling of maliciously crafted fonts, which can lead to unexpected application termination or corruption of process memory. Although the exact exploitation vector remains unclear and remote code execution has not been confirmed, memory corruption vulnerabilities often carry risks of privilege escalation or arbitrary code execution if exploited. The flaw affects a wide range of Apple devices due to the shared Font Parser codebase across platforms. Apple’s typical post-major-release update pattern includes functional fixes and security patches, with this update being notable for addressing a security issue. No known exploits have been detected in the wild, indicating that attackers have not yet leveraged this vulnerability. The updates for WatchOS and tvOS do not address this security issue, suggesting these platforms are not affected. The vulnerability’s impact is primarily on application stability and memory integrity, which could be leveraged in targeted attacks if combined with other vulnerabilities. The broad affected version range necessitates patching across multiple Apple OS versions to ensure comprehensive protection.

For European organizations, the vulnerability poses risks primarily related to application crashes and potential memory corruption on Apple devices. This can lead to denial of service conditions or, in worst-case scenarios, could be a stepping stone for more severe exploits such as remote code execution or privilege escalation if combined with other vulnerabilities. Organizations relying heavily on Apple ecosystems—such as enterprises using iPhones, iPads, Macs, and visionOS devices for critical business operations—may experience operational disruptions if exploited. The lack of known exploits reduces immediate risk but does not eliminate the threat, especially given the widespread use of Apple products in Europe. Sectors such as finance, healthcare, and government, which often use Apple devices for secure communications and operations, could face increased risk if attackers develop exploit code. Additionally, memory corruption vulnerabilities can be leveraged in sophisticated attack chains, making timely patching essential to maintain confidentiality, integrity, and availability of systems. The medium severity rating reflects moderate risk but underscores the importance of proactive mitigation to prevent escalation.

European organizations should implement the following specific mitigation steps: 1) Prioritize deployment of Apple’s security updates for iOS 18 and 26, macOS Sonoma (14) and later, and visionOS 26 across all managed devices to close the vulnerability. 2) Conduct an inventory of Apple devices in use to ensure all affected versions are identified and updated promptly. 3) Employ endpoint management solutions capable of enforcing update policies and monitoring patch compliance on Apple devices. 4) Educate users to avoid opening untrusted font files or documents that may contain malicious fonts, especially from unknown sources or email attachments. 5) Monitor system logs and application crash reports for unusual behavior that may indicate exploitation attempts. 6) Integrate network-level protections to detect and block delivery of suspicious font files or payloads in email and web traffic. 7) Coordinate with Apple support and security advisories to stay informed about any emerging exploit reports or additional patches. 8) For organizations using visionOS devices, ensure updates are applied despite the lower profile of this platform. 9) Review and update incident response plans to include scenarios involving memory corruption or application crashes on Apple devices. 10) Consider deploying application whitelisting and sandboxing technologies to limit the impact of potential exploitation.