CVE-2017-7184 in Linux
Summary
by MITRE
The linux-image-* package 4.8.0.41.52 for the Linux kernel on Ubuntu 16.10 allows local users to obtain root privileges or cause a denial of service (heap-based out-of-bounds access) via unspecified vectors, as demonstrated during a Pwn2Own competition at CanSecWest 2017.
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Analysis
by VulDB Data Team • 09/10/2020
The vulnerability identified as CVE-2017-7184 represents a critical heap-based out-of-bounds access flaw within the Linux kernel's linux-image-* package version 4.8.0.41.52 specifically affecting Ubuntu 16.10 systems. This vulnerability was particularly significant as it was demonstrated during the prestigious Pwn2Own competition at CanSecWest 2017, where researchers successfully exploited the flaw to achieve privilege escalation to root level access. The issue stems from improper bounds checking within kernel memory management routines, creating a scenario where malicious code can manipulate heap memory structures beyond their allocated boundaries. Such vulnerabilities are classified under CWE-121 as heap-based buffer overflow conditions, which directly enable attackers to execute arbitrary code with elevated privileges. The vulnerability's exploitation potential aligns with attack techniques described in the MITRE ATT&CK framework under privilege escalation tactics, specifically leveraging kernel-level vulnerabilities to gain system-level control.
The technical implementation of this vulnerability involves memory corruption within kernel space heap management where insufficient input validation allows attackers to manipulate memory allocation patterns. When the vulnerable kernel components process certain inputs, they fail to properly validate array indices or memory boundaries, leading to heap corruption that can be leveraged for arbitrary code execution. The out-of-bounds access occurs during memory allocation or deallocation operations where kernel functions do not properly verify that memory access operations remain within legitimate heap boundaries. This type of vulnerability typically arises from inadequate bounds checking in kernel memory management subsystems, particularly affecting the kernel's slab allocator or other heap management components. The specific vectors that trigger this vulnerability were not fully disclosed publicly to prevent widespread exploitation, but they likely involved crafted inputs to kernel interfaces or system calls that manipulate memory allocation structures. The vulnerability's classification as a heap-based out-of-bounds access aligns with common exploitation patterns found in kernel security research and represents a fundamental failure in memory safety mechanisms.
The operational impact of CVE-2017-7184 extends beyond simple privilege escalation to encompass potential system compromise and denial of service conditions. When exploited successfully, local users can gain root privileges without requiring authentication, effectively providing complete system control to any user who can execute the exploitation payload. This represents a severe security risk for systems where local access is not properly restricted, as it allows attackers to bypass all standard user permission controls and access sensitive system resources. The vulnerability's potential for denial of service exists as well, since heap corruption can cause kernel panics or system crashes when the memory corruption is severe enough to destabilize kernel memory management. Additionally, the vulnerability's exploitation during a high-profile security competition demonstrates its real-world applicability and the ease with which skilled attackers can leverage such flaws. The impact on Ubuntu 16.10 systems was particularly severe as this version was still actively supported and widely deployed in enterprise environments, making the vulnerability a significant concern for system administrators and security teams responsible for maintaining kernel security.
Mitigation strategies for CVE-2017-7184 primarily focus on immediate kernel updates and system hardening measures. The most effective solution involves applying the official kernel security patches provided by Ubuntu, which address the specific memory bounds checking issues within the affected kernel versions. System administrators should prioritize updating to kernel versions that contain fixes for this vulnerability, typically those released after the vulnerability disclosure. Additional mitigations include implementing proper access controls to limit local user privileges, monitoring for suspicious kernel memory operations, and applying kernel lockdown mechanisms where appropriate. The vulnerability's exploitation requires local access, so restricting local user accounts and implementing proper user privilege management can significantly reduce the attack surface. Organizations should also consider deploying kernel module signing policies and implementing runtime memory protection mechanisms such as stack canaries or memory protection keys. The remediation process should include thorough testing of kernel updates in controlled environments before deployment to production systems, as kernel updates can sometimes introduce compatibility issues with existing system configurations. Security monitoring should focus on detecting unusual memory allocation patterns or kernel-level activities that might indicate exploitation attempts, as the vulnerability's exploitation typically involves specific kernel memory corruption patterns that can be detected through proper system monitoring.