CVE-2023-41991 is a certificate validation vulnerability affecting Apple iOS and iPadOS versions prior to 16.7, as well as macOS versions before Ventura 13.6. The core issue lies in a flaw in the signature validation process, specifically related to certificate validation (CWE-295), which allows a maliciously crafted app to bypass the normal signature verification mechanisms. This bypass means that an attacker could potentially install or execute unauthorized applications that appear to be legitimately signed, undermining the platform’s app integrity guarantees. The vulnerability requires local access and user interaction, meaning an attacker must convince a user to install or run the malicious app. Apple has acknowledged reports of active exploitation attempts against vulnerable iOS versions, though no widespread campaigns have been confirmed. The vulnerability does not impact confidentiality or availability directly but poses a significant risk to the integrity of the device’s software environment, potentially enabling further malicious activities such as persistence, privilege escalation, or data manipulation. The CVSS 3.1 base score is 5.5, reflecting a medium severity level with an attack vector limited to local, low attack complexity, no privileges required, and user interaction needed. The issue was addressed in iOS and iPadOS 16.7 and macOS Ventura 13.6 through improved certificate validation and signature verification processes.

For European organizations, this vulnerability poses a risk primarily to the integrity of Apple mobile devices and potentially macOS systems if used in the enterprise environment. Compromised devices could allow attackers to run unauthorized applications that may perform malicious activities such as data tampering, espionage, or lateral movement within corporate networks. Given the widespread use of Apple devices in sectors like finance, healthcare, and government across Europe, exploitation could lead to breaches of sensitive data or disruption of critical services. The requirement for user interaction and local access somewhat limits mass exploitation but does not eliminate targeted attacks, especially spear-phishing or social engineering campaigns aimed at high-value individuals or employees with privileged access. The vulnerability could also undermine trust in app supply chains and enterprise app deployment mechanisms, complicating device management and security assurance. Organizations relying on iOS and iPadOS devices should consider the risk of undetected malicious apps bypassing signature checks, which could facilitate persistent threats or insider attacks.

European organizations should immediately ensure all Apple devices are updated to iOS and iPadOS 16.7 or later, and macOS devices to Ventura 13.6 or later, as these versions contain the necessary fixes. Beyond patching, organizations should enforce strict mobile device management (MDM) policies that restrict app installation to trusted sources only, such as the official Apple App Store or enterprise app stores with rigorous vetting. Implementing application allowlisting can reduce the risk of unauthorized apps running even if signature validation is bypassed. User training to recognize phishing and social engineering attempts is critical, as user interaction is required for exploitation. Monitoring device logs and network traffic for unusual app installation or behavior can help detect potential exploitation attempts. Additionally, organizations should review and tighten their endpoint security controls on Apple devices, including the use of endpoint detection and response (EDR) tools that support iOS/iPadOS. Regular audits of installed applications and certificate trust stores can help identify anomalies. Finally, organizations should maintain an incident response plan that includes procedures for compromised mobile devices.