CVE-2016-8637 in dracut
Summary
by MITRE
A local information disclosure issue was found in dracut before 045 when generating initramfs images with world-readable permissions when 'early cpio' is used, such as when including microcode updates. Local attacker can use this to obtain sensitive information from these files, such as encryption keys or credentials.
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Analysis
by VulDB Data Team • 04/28/2023
The vulnerability identified as CVE-2016-8637 represents a critical local information disclosure flaw within the dracut initramfs generation framework. This issue specifically affects versions of dracut prior to 045 and manifests when the system generates initramfs images with world-readable permissions during the 'early cpio' process. The vulnerability arises from improper permission handling during the creation of early boot image files, creating an attack surface that allows local adversaries to access sensitive data stored within these files.
The technical flaw stems from the improper management of file permissions during the initramfs generation process, where sensitive information including encryption keys and authentication credentials may be written to files with overly permissive access controls. When microcode updates are included in the initramfs image, the 'early cpio' mechanism creates files that are accessible to all users on the system. This permission misconfiguration allows local attackers to read these files directly from the filesystem, bypassing normal access controls and exposing confidential data that should remain protected during the boot process.
From an operational impact perspective, this vulnerability enables local attackers to obtain sensitive information that could compromise system security and confidentiality. The exposure of encryption keys and credentials within the initramfs image creates potential for privilege escalation and further system compromise. Attackers can leverage this information to gain unauthorized access to encrypted volumes, network credentials, or other sensitive data that was intended to remain protected during the early boot phase of system initialization. This vulnerability particularly affects systems that utilize microcode updates in their boot process, making it relevant to a significant portion of enterprise and server environments.
The vulnerability aligns with CWE-276, which addresses improper file permissions, and represents a classic case of insecure default configuration in system initialization tools. From an attack perspective, this issue maps to ATT&CK technique T1003.002 for Credential Dumping and T1068 for Local Privilege Escalation, as attackers can exploit the exposed information to escalate privileges or gain access to additional system resources. The attack vector is particularly concerning because it requires no network access or external exploitation, relying solely on local file system access to obtain sensitive information.
Mitigation strategies for CVE-2016-8637 include upgrading to dracut version 045 or later, which addresses the permission handling issue in initramfs generation. System administrators should also implement proper file permission controls and audit the initramfs generation process to ensure sensitive data is not exposed through overly permissive file access. Additionally, organizations should consider implementing automated monitoring for unauthorized access to initramfs files and establish regular security audits of boot image configurations to prevent similar vulnerabilities from persisting in system environments.