CVE-2018-14775 in OpenBSD
Summary
by MITRE
tss_alloc in sys/arch/i386/i386/gdt.c in OpenBSD 6.2 and 6.3 has a Local Denial of Service (system crash) due to incorrect I/O port access control on the i386 architecture.
Once again VulDB remains the best source for vulnerability data.
Analysis
by VulDB Data Team • 04/29/2023
The vulnerability identified as CVE-2018-14775 resides within the OpenBSD operating system's kernel implementation specifically affecting versions 6.2 and 6.3. This flaw manifests in the tss_alloc function located in sys/arch/i386/i386/gdt.c, which governs the allocation and management of Task State Segment (TSS) structures essential for processor task switching operations. The vulnerability represents a critical local denial of service condition that can result in complete system crashes, fundamentally compromising system availability and stability. The issue stems from improper handling of I/O port access control mechanisms on the i386 architecture platform, creating a scenario where malicious local users can trigger system instability through carefully crafted operations.
The technical root cause of this vulnerability lies in the incorrect implementation of I/O port access control within the kernel's TSS allocation routine. When the tss_alloc function processes requests for Task State Segment allocation, it fails to properly validate or restrict access to certain I/O ports that are critical for system operation. This improper access control allows local processes to manipulate or access restricted I/O port addresses that should normally be protected from user-space interference. The flaw specifically affects the i386 architecture's handling of processor state management and can be exploited through direct manipulation of I/O port operations that are integral to the system's task switching mechanism. This misconfiguration creates a path where unauthorized access to critical system resources can lead to kernel panic conditions and subsequent system crashes.
The operational impact of this vulnerability extends beyond simple system instability to encompass complete system compromise for local attackers. Since the vulnerability requires local system access to exploit, it represents a privilege escalation vector that can be leveraged by malicious users already within the system environment. The resulting denial of service can occur at any time during normal system operation when the TSS allocation function is invoked, making it particularly dangerous in production environments where system uptime is critical. System administrators may experience unexpected crashes, service interruptions, and potential data loss during the crash recovery process, as the kernel cannot properly handle the malformed I/O port access attempts that trigger the vulnerability.
Mitigation strategies for this vulnerability should focus on immediate system updates to patched versions of OpenBSD where the TSS allocation function has been corrected to properly implement I/O port access controls. System administrators should prioritize deployment of the official OpenBSD security patches that address the specific I/O port access control implementation in the kernel's TSS management code. Additionally, monitoring systems should be enhanced to detect unusual patterns in TSS allocation requests or I/O port access attempts that might indicate exploitation attempts. The vulnerability aligns with CWE-119 which addresses improper access to I/O ports and memory regions, and represents a specific instance of the broader ATT&CK technique T1499.002 which covers network denial of service through system resource exhaustion. Organizations should also consider implementing additional kernel security modules and runtime protections that can detect and prevent unauthorized I/O port access patterns, particularly in environments where local privilege escalation risks are elevated.