CVE-2024-40867 is a vulnerability identified in Apple iOS and iPadOS that stems from improper handling of custom URL schemes within the Web Content sandbox environment. The Web Content sandbox is a security mechanism designed to isolate web content from the rest of the system, preventing malicious web content from accessing sensitive device resources. This vulnerability allows a remote attacker to bypass these sandbox restrictions by exploiting flaws in the input validation of custom URL schemes. Specifically, the attacker crafts a malicious URL that, when processed by the vulnerable system, can break out of the sandbox and execute arbitrary code or perform unauthorized actions on the device. The flaw was addressed in iOS and iPadOS version 18.1 through improved input validation mechanisms that prevent malformed or malicious URLs from triggering the sandbox escape. The CVSS v3.1 score of 8.8 reflects the vulnerability's high impact: it can be exploited remotely over the network without any privileges (AV:N/PR:N), but requires user interaction (UI:R), such as clicking a link. The scope is unchanged (S:U), but the impact on confidentiality, integrity, and availability is high (C:H/I:H/A:H), meaning an attacker could fully compromise the device. No public exploits have been observed yet, but the nature of the vulnerability makes it a significant threat vector, especially given the widespread use of iOS and iPadOS devices in enterprise and government environments.

For European organizations, this vulnerability poses a substantial risk due to the widespread adoption of Apple mobile devices across both private and public sectors. A successful exploitation could lead to unauthorized access to sensitive corporate or governmental data, disruption of critical services, and potential lateral movement within networks if devices are used as entry points. Sectors such as finance, healthcare, government, and critical infrastructure are particularly vulnerable due to the high value of data and services they manage. The requirement for user interaction means phishing or social engineering campaigns could be used to trigger the exploit, increasing the risk in environments with less stringent user awareness training. Additionally, the ability to break out of the Web Content sandbox could enable attackers to install persistent malware, steal credentials, or manipulate device functionality, severely impacting operational continuity and data privacy compliance obligations under regulations like GDPR.

European organizations should prioritize immediate deployment of iOS and iPadOS 18.1 updates to all managed devices to remediate this vulnerability. Beyond patching, organizations should implement strict controls on the handling of custom URL schemes, including restricting or monitoring the use of untrusted or unknown URL schemes within enterprise applications. User awareness training should be enhanced to reduce the risk of phishing attacks that could trigger the exploit. Mobile Device Management (MDM) solutions can be configured to limit app installations and control web content rendering behaviors. Network-level protections such as web filtering and URL reputation services can help block access to malicious links. Additionally, organizations should audit and monitor device logs for unusual behaviors indicative of sandbox escapes or unauthorized code execution. Incident response plans should be updated to include scenarios involving mobile device compromise via sandbox escape vulnerabilities.