CVE-2016-4997 in Linux
Summary
by MITRE • 01/25/2023
The compat IPT_SO_SET_REPLACE and IP6T_SO_SET_REPLACE setsockopt implementations in the netfilter subsystem in the Linux kernel before 4.6.3 allow local users to gain privileges or cause a denial of service (memory corruption) by leveraging in-container root access to provide a crafted offset value that triggers an unintended decrement.
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Analysis
by VulDB Data Team • 11/11/2024
The vulnerability identified as CVE-2016-4997 resides within the netfilter subsystem of the Linux kernel, specifically affecting versions prior to 4.6.3. This flaw manifests in the implementation of compat IPT_SO_SET_REPLACE and IP6T_SO_SET_REPLACE setsockopt operations, which are designed to handle socket options for packet filtering and manipulation. The vulnerability represents a critical privilege escalation vector that can be exploited by local users who have already gained root access within a container environment. The technical nature of this vulnerability is rooted in improper input validation and memory management within the kernel's networking subsystem, creating a pathway for malicious actors to manipulate kernel memory structures through crafted offset values.
The core technical flaw involves an unintended decrement operation that occurs when processing crafted offset values in the netfilter setsockopt implementations. When a local user with container root privileges provides a specially crafted offset value, the kernel's processing logic performs an incorrect decrement operation that leads to memory corruption. This memory corruption can manifest in various ways including kernel panic, system crashes, or more critically, privilege escalation that allows attackers to gain higher privileges than initially granted. The vulnerability is particularly dangerous because it operates within the kernel space, where any memory corruption can lead to complete system compromise. This flaw aligns with CWE-121, which describes stack-based buffer overflow conditions, and demonstrates how improper integer handling can lead to memory corruption vulnerabilities.
The operational impact of CVE-2016-4997 extends beyond simple denial of service scenarios to encompass potential privilege escalation and system compromise. In containerized environments where users may have root access to their containers but not to the host system, this vulnerability provides a means to escape container boundaries and gain elevated privileges on the underlying host. The attack requires only local access within a container, making it particularly concerning for cloud environments and multi-tenant systems where container isolation is expected to prevent privilege escalation. The vulnerability affects systems running Linux kernel versions before 4.6.3, which were widely deployed across various enterprise and cloud environments, amplifying the potential impact.
Mitigation strategies for CVE-2016-4997 primarily involve upgrading to Linux kernel version 4.6.3 or later, where the vulnerability has been patched through proper input validation and memory handling. Organizations should implement comprehensive patch management processes to ensure all systems running affected kernel versions receive timely updates. Additionally, network administrators should consider implementing additional security controls such as mandatory access controls and container isolation measures to limit the potential impact of such vulnerabilities. The ATT&CK framework categorizes this vulnerability under privilege escalation techniques, specifically targeting kernel-level exploits that leverage memory corruption vulnerabilities. System administrators should also consider monitoring for unusual network filtering operations and implementing least privilege principles for container environments to minimize the potential attack surface. Organizations utilizing container technologies should perform regular security assessments and maintain updated security baselines to prevent exploitation of such kernel-level vulnerabilities.