CVE-2013-5666 in FreeBSD
Summary
by MITRE
The sendfile system-call implementation in sys/kern/uipc_syscalls.c in the kernel in FreeBSD 9.2-RC1 and 9.2-RC2 does not properly pad transmissions, which allows local users to obtain sensitive information (kernel memory) via a length greater than the length of the file.
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Analysis
by VulDB Data Team • 05/24/2021
The vulnerability identified as CVE-2013-5666 represents a critical information disclosure flaw within the FreeBSD operating system kernel, specifically affecting versions 9.2-RC1 and 9.2-RC2. This issue resides in the sendfile system call implementation located in sys/kern/uipc_syscalls.c, where the kernel fails to properly pad data transmissions when handling file transfers. The flaw exploits a fundamental weakness in how the kernel manages memory copying operations during network file transmission, creating an opportunity for local attackers to access kernel memory contents through carefully crafted requests.
The technical implementation of this vulnerability stems from improper handling of buffer boundaries during the sendfile system call execution. When a local user submits a request with a transmission length that exceeds the actual file size, the kernel's sendfile implementation does not correctly pad the data transmission to maintain proper memory alignment. This padding failure results in the kernel inadvertently exposing uninitialized memory contents, including potentially sensitive kernel data structures, stack contents, and other confidential information that should remain protected from user-space access. The vulnerability operates at the kernel level, making it particularly dangerous as it bypasses normal user-space memory protection mechanisms.
The operational impact of CVE-2013-5666 extends beyond simple information disclosure, as it provides attackers with access to kernel memory that may contain credentials, encryption keys, or other sensitive operational data. This local privilege escalation vector allows attackers to gain insights into the kernel's internal state, potentially enabling more sophisticated attacks such as kernel exploitation or privilege escalation to root access. The vulnerability affects systems running FreeBSD 9.2-RC1 and 9.2-RC2, which were release candidates containing the flawed implementation, and represents a significant security risk for any system where local users have access to the affected kernel interface.
Security mitigations for this vulnerability primarily involve applying the official FreeBSD security patches that address the improper padding in the sendfile system call implementation. System administrators should immediately upgrade to patched versions of FreeBSD 9.2 or later releases that contain the corrected kernel code. Additionally, organizations should consider implementing network segmentation and access controls to limit local user access to systems running affected kernel versions. The vulnerability aligns with CWE-200, which addresses improper output handling, and can be categorized under ATT&CK technique T1005 for data from local system, demonstrating how local users can leverage kernel-level flaws to access sensitive information. Organizations should also conduct thorough security assessments to identify systems running vulnerable kernel versions and implement comprehensive monitoring for potential exploitation attempts targeting this specific vulnerability.