CVE-2018-7754 in Linux
Summary
by MITRE
The aoedisk_debugfs_show function in drivers/block/aoe/aoeblk.c in the Linux kernel through 4.16.4rc4 allows local users to obtain sensitive address information by reading "ffree: " lines in a debugfs file.
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Analysis
by VulDB Data Team • 03/14/2020
The vulnerability identified as CVE-2018-7754 resides within the Linux kernel's aoedisk_debugfs_show function located in drivers/block/aoe/aoeblk.c. This issue affects kernel versions through 4.16.4rc4 and represents a significant information disclosure flaw that exposes sensitive memory addresses to local attackers. The problem manifests when users read debugfs files associated with the aoe (ATA over Ethernet) block driver, specifically targeting the "ffree: " lines that contain memory address information. This type of vulnerability falls under the CWE-200 category of Information Exposure and represents a classic case of sensitive data leakage through improper access control mechanisms.
The technical implementation of this vulnerability stems from the debugfs interface not properly sanitizing memory addresses before exposing them to userspace. The aoe block driver utilizes debugfs for diagnostic purposes, but the aoedisk_debugfs_show function fails to strip or obfuscate memory addresses that are inadvertently included in the debug output. When local users access these debugfs entries, they can read the "ffree: " lines that contain kernel virtual addresses, which can be leveraged for advanced exploitation techniques. This flaw represents a direct violation of the principle of least privilege and demonstrates inadequate security considerations in kernel debug interfaces.
The operational impact of CVE-2018-7754 extends beyond simple information disclosure, as the leaked memory addresses can significantly aid attackers in developing more sophisticated exploits. Knowledge of kernel memory layouts enables attackers to perform address space layout randomization (ASLR) bypass techniques, making subsequent exploitation attempts more successful. The vulnerability affects systems running Linux kernel versions up to 4.16.4rc4, which includes numerous enterprise and server deployments where the aoe block driver is utilized for storage networking. This exposure creates a persistent risk for systems that do not properly restrict debugfs access or implement adequate access controls for kernel debugging interfaces.
Mitigation strategies for this vulnerability involve multiple layers of defense including kernel version updates, access control restrictions, and operational hardening measures. System administrators should prioritize upgrading to kernel versions that contain the fix for this vulnerability, which was addressed in kernel versions beyond 4.16.4rc4. The debugfs interface should be secured by implementing proper access controls that restrict read permissions to authorized users only, as outlined in the NIST SP 800-53 security controls for operating systems. Additionally, organizations should implement monitoring for unusual debugfs access patterns and consider disabling debugfs interfaces in production environments where they are not actively required for troubleshooting. The ATT&CK framework categorizes this vulnerability under T1059.001 for command and script interpreter and T1068 for exploit for privilege escalation, highlighting its potential for advancing attacker capabilities within compromised systems.