CVE-2018-6919 in FreeBSD
Summary
by MITRE
In FreeBSD before 11.1-STABLE, 11.1-RELEASE-p9, 10.4-STABLE, 10.4-RELEASE-p8 and 10.3-RELEASE-p28, due to insufficient initialization of memory copied to userland, small amounts of kernel memory may be disclosed to userland processes. Unprivileged users may be able to access small amounts privileged kernel data.
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Analysis
by VulDB Data Team • 02/09/2021
This vulnerability exists in FreeBSD operating systems prior to specific stable and release versions, representing a classic information disclosure flaw that allows unprivileged user processes to access sensitive kernel memory contents. The issue stems from inadequate memory initialization during data transfer operations between kernel and user space, creating a pathway for unauthorized data exposure that violates fundamental security principles of operating system isolation.
The technical flaw manifests when the kernel copies memory regions to userland processes without properly zeroing or initializing the memory areas before transmission. This insufficient initialization means that portions of kernel memory, which should remain protected and inaccessible to regular userspace applications, may contain residual data from previous operations or kernel structures. The vulnerability affects multiple FreeBSD release lines including 10.3, 10.4, and 11.1, indicating it was present across several major versions and likely introduced during a specific code modification or memory management routine.
From an operational impact perspective, this vulnerability enables unprivileged users to potentially extract small amounts of privileged kernel data, which could include sensitive information such as cryptographic keys, system configuration details, or other confidential kernel structures. The disclosed information, while limited in quantity, could provide attackers with valuable insights for further exploitation attempts or aid in crafting more sophisticated attacks against the system. This type of information disclosure vulnerability aligns with CWE-200, which categorizes weaknesses related to improper information exposure, and can be leveraged by adversaries following the ATT&CK tactic of reconnaissance to gather intelligence about the target system.
The security implications extend beyond simple data leakage, as the exposure of kernel memory can reveal patterns and structures that might aid in privilege escalation or other advanced attack vectors. Attackers could potentially use this information to understand kernel memory layout, identify security mechanisms, or discover other vulnerabilities that might not be immediately apparent through standard reconnaissance techniques. This vulnerability demonstrates the critical importance of proper memory management practices in kernel code and the potential consequences of insufficient input validation and output sanitization in privileged code paths.
Mitigation strategies should focus on updating to the patched versions of FreeBSD that address this specific memory initialization issue, ensuring that all systems are running the latest stable releases that contain the necessary security fixes. Organizations should also implement monitoring for unusual memory access patterns and consider additional security controls such as kernel memory protection mechanisms and privilege separation techniques. The vulnerability highlights the need for comprehensive code review practices, particularly focusing on kernel-space memory handling and the principle of least privilege in data transfer operations between kernel and user space components.