CVE-2016-1887 in FreeBSD
Summary
by MITRE
Integer signedness error in the sockargs function in sys/kern/uipc_syscalls.c in FreeBSD 10.1 before p34, 10.2 before p17, and 10.3 before p3 allows local users to cause a denial of service (memory overwrite and kernel panic) or gain privileges via a negative buflen argument, which triggers a heap-based buffer overflow.
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Analysis
by VulDB Data Team • 07/07/2024
The vulnerability identified as CVE-2016-1887 represents a critical integer signedness error within the FreeBSD operating system kernel, specifically affecting versions prior to designated patch levels. This flaw exists within the sockargs function located in sys/kern/uipc_syscalls.c, which handles socket argument processing during system calls. The vulnerability manifests when a negative buflen argument is passed to the socket system call interface, creating a scenario where the kernel fails to properly validate input parameters before proceeding with memory allocation operations.
The technical implementation of this vulnerability stems from improper handling of signed integer values during buffer size calculations. When a negative value is provided for the buflen parameter, the kernel's sockargs function fails to detect this invalid input and proceeds with memory allocation based on the negative value. This leads to a heap-based buffer overflow condition where the kernel attempts to allocate memory in an unexpected manner, causing memory corruption that can result in either a kernel panic or more severe privilege escalation opportunities. The flaw operates at the kernel level and requires local user access to exploit, making it particularly dangerous in multi-user environments.
From an operational impact perspective, this vulnerability presents a significant risk to FreeBSD systems as it can be exploited to either crash the system through denial of service or potentially escalate privileges to kernel level access. The memory overwrite condition can cause unpredictable behavior including system crashes, data corruption, or in some cases, allow attackers to execute arbitrary code with elevated privileges. This vulnerability directly impacts the integrity and availability of FreeBSD systems, particularly those running affected versions in production environments where local access might be obtained through legitimate user accounts or compromised services.
The exploitation of this vulnerability aligns with several attack patterns documented in the MITRE ATT&CK framework, particularly focusing on privilege escalation and denial of service techniques. The vulnerability can be classified under CWE-191, Integer Underflow or Wraparound, which describes the condition where an integer value becomes smaller than its minimum representable value. Additionally, the heap-based buffer overflow component relates to CWE-119, which encompasses memory safety issues including buffer overflows that can lead to arbitrary code execution. Organizations should implement immediate patching strategies to address this vulnerability, as the risk of exploitation increases with the availability of the vulnerability details in public repositories and security research communities. The recommended mitigation approach involves upgrading to patched versions of FreeBSD where the integer validation has been properly implemented to prevent negative values from being processed as buffer sizes.