CVE-2005-1036 in FreeBSD
Summary
by MITRE
FreeBSD 5.x to 5.4 on AMD64 does not properly initialize the IO permission bitmap used to allow user access to certain hardware, which allows local users to bypass intended access restrictions to cause a denial of service, obtain sensitive information, and possibly gain privileges.
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Analysis
by VulDB Data Team • 07/02/2019
The vulnerability identified as CVE-2005-1036 represents a critical flaw in the FreeBSD operating system version 5.x through 5.4 specifically on AMD64 architecture platforms. This issue stems from improper initialization of the IO permission bitmap, a critical component that governs user-level access to hardware resources and system peripherals. The IO permission bitmap serves as a fundamental security mechanism within the x86 architecture, controlling which processes can directly access hardware I/O ports and memory-mapped registers. When this bitmap fails to initialize correctly, it creates a dangerous security boundary that can be exploited by malicious local users to circumvent the intended access controls that protect system integrity and confidentiality.
The technical flaw manifests in the kernel's handling of the IO permission bitmap during system initialization and context switching operations on AMD64 processors. This misconfiguration allows local attackers to manipulate the bitmap in such a way that they can gain unauthorized access to hardware resources that should normally be restricted to kernel-level operations. The vulnerability specifically affects the virtual memory management subsystem and the hardware abstraction layer, where the kernel fails to properly set up the I/O permission bitmap before user processes are allowed to execute. This creates a scenario where malicious code can potentially access sensitive hardware registers, read protected memory regions, and manipulate system resources that should remain isolated from user-space applications. The flaw operates at the privilege level boundary, where user processes can inadvertently gain access to kernel-level hardware control mechanisms through the improperly initialized bitmap.
The operational impact of this vulnerability extends beyond simple denial of service conditions to encompass serious security implications including information disclosure and privilege escalation. Local users who exploit this vulnerability can cause system instability through denial of service attacks by manipulating hardware resources, but more critically they can extract sensitive information from system memory and hardware registers that should remain protected. The potential for privilege escalation exists because the flawed IO permission bitmap allows unauthorized access to hardware components that may contain system credentials, cryptographic keys, or other sensitive data. This vulnerability directly violates the principle of least privilege and can lead to complete system compromise if exploited by a determined attacker. The attack surface is particularly concerning given that it affects a widely used operating system version and architecture combination, potentially exposing numerous systems to exploitation.
Mitigation strategies for CVE-2005-1036 require immediate system updates to patched FreeBSD versions that properly initialize the IO permission bitmap and correct the underlying kernel initialization routines. System administrators should implement the latest security patches from the FreeBSD project, which address the specific initialization flaw in the IO permission bitmap handling code. Additional defensive measures include implementing strict access controls for system resources, monitoring for unauthorized hardware access patterns, and ensuring that system updates are applied promptly to prevent exploitation. The vulnerability aligns with CWE-264, which addresses permissions, privileges, and access control issues, and represents a classic example of how improper initialization of security-critical data structures can lead to severe system compromise. Organizations should also consider implementing intrusion detection systems that can monitor for suspicious hardware access patterns and establish comprehensive incident response procedures to address potential exploitation attempts. This vulnerability demonstrates the critical importance of proper kernel initialization and the potential consequences when fundamental security mechanisms fail to function correctly.