CVE-2019-8516 in macOS
Summary
by MITRE
A validation issue was addressed with improved logic. This issue is fixed in iOS 12.2, macOS Mojave 10.14.4, tvOS 12.2, watchOS 5.2. Processing a maliciously crafted string may lead to a denial of service.
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Analysis
by VulDB Data Team • 08/08/2023
The vulnerability identified as CVE-2019-8516 represents a validation issue that was successfully addressed through improved logical processing within Apple's operating systems. This flaw existed in multiple platform versions including iOS 12.1 and earlier, macOS Mojave 10.14.3 and earlier, tvOS 12.1 and earlier, and watchOS 5.1 and earlier. The security issue stems from inadequate input validation mechanisms that failed to properly sanitize or verify string data structures before processing. According to industry standards, this vulnerability maps to CWE-20, which specifically addresses "Improper Input Validation" as a fundamental weakness in software security design. The flaw demonstrates how insufficient validation logic can create exploitable conditions that compromise system stability and availability.
The technical execution of this vulnerability occurs when the affected operating systems process a maliciously crafted string that triggers improper validation behavior. This type of input manipulation can cause the system to enter an unexpected state during string processing operations, ultimately leading to a denial of service condition. The vulnerability's impact is specifically focused on system stability rather than direct privilege escalation or data compromise, though the denial of service aspect can severely impact user experience and system functionality. The root cause lies in the lack of proper bounds checking, format validation, or sanitization procedures within the string processing pipelines of these operating systems. From an attacker's perspective, this represents a relatively low-effort vector for causing system disruption, as it requires only the construction of a specific malformed string to trigger the problematic code path.
The operational impact of CVE-2019-8516 extends beyond simple service interruption to potentially affect user productivity and system reliability across Apple's ecosystem. When exploited, the vulnerability can cause applications or system services to crash or become unresponsive, forcing users to restart their devices or potentially disrupting critical operations. This is particularly concerning in enterprise environments where Apple devices are extensively deployed, as coordinated exploitation could lead to widespread service degradation. The vulnerability affects all supported Apple platforms, creating a consistent risk profile across mobile, desktop, and embedded systems, which increases the overall attack surface and complicates remediation efforts. The fix implemented by Apple in versions 12.2, 10.14.4, 12.2, and 5.2 respectively demonstrates the company's approach to addressing validation weaknesses through improved code logic and enhanced input sanitization procedures.
Mitigation strategies for CVE-2019-8516 primarily focus on immediate system updates to the patched versions mentioned in the advisory. System administrators should prioritize deployment of the relevant security updates across all managed devices, particularly in environments where device availability is critical. The vulnerability's nature suggests that monitoring for unusual application crashes or system instability patterns could serve as an early detection mechanism, though this is not a substitute for proper patch management. Organizations should also consider implementing network-based monitoring to detect potential exploitation attempts through malformed string inputs, particularly in environments where Apple devices connect to untrusted networks or process unverified user inputs. The ATT&CK framework categorizes this type of vulnerability under T1499, which deals with "Endpoint Denial of Service" techniques, emphasizing the importance of maintaining system stability and preventing resource exhaustion through proper input validation. Regular security assessments should include verification that string processing functions properly validate all inputs and that appropriate error handling mechanisms are in place to prevent system instability.