CVE-2016-4998 in Android
Summary
by MITRE
The IPT_SO_SET_REPLACE setsockopt implementation in the netfilter subsystem in the Linux kernel before 4.6 allows local users to cause a denial of service (out-of-bounds read) or possibly obtain sensitive information from kernel heap memory by leveraging in-container root access to provide a crafted offset value that leads to crossing a ruleset blob boundary.
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Analysis
by VulDB Data Team • 09/15/2022
The vulnerability identified as CVE-2016-4998 represents a critical flaw in the Linux kernel's netfilter subsystem that affects versions prior to 4.6. This issue manifests through the IPT_SO_SET_REPLACE setsockopt implementation, which governs how iptables rules are replaced within the kernel's network filtering framework. The vulnerability specifically targets local users who possess in-container root access, creating a scenario where privilege escalation opportunities exist within containerized environments where such access is already granted. The flaw operates by exploiting improper bounds checking during the processing of crafted offset values that are passed to the setsockopt function, leading to memory access violations that can result in system instability or information disclosure.
The technical implementation of this vulnerability stems from inadequate validation of user-supplied offset parameters within the kernel's netfilter code path. When a crafted offset value is provided through the IPT_SO_SET_REPLACE ioctl command, the kernel fails to properly verify that the offset remains within the bounds of the allocated ruleset blob structure. This oversight creates a scenario where an attacker can cause an out-of-bounds read operation that accesses kernel heap memory beyond the intended boundaries. The vulnerability falls under the CWE-129 weakness category, specifically addressing improper validation of the lower bound of a buffer or index, and can be classified as a memory safety issue within the kernel's network filtering subsystem. The flaw represents a classic case of insufficient input validation leading to memory corruption that can be exploited for information disclosure or system denial of service.
The operational impact of CVE-2016-4998 extends beyond simple denial of service conditions to potentially enable information leakage from kernel memory spaces. In containerized environments where root access is already available, an attacker can leverage this vulnerability to extract sensitive kernel data that might include cryptographic keys, credential information, or other confidential system details. The vulnerability's exploitation requires local access with root privileges within a container, but the implications are significant as it can compromise the security isolation that containers are designed to provide. This weakness aligns with the ATT&CK technique T1068 which describes the use of local privilege escalation to gain higher-level access within a system. The vulnerability essentially undermines the security model of containerized applications by allowing information disclosure that can be used to further compromise the system.
Mitigation strategies for CVE-2016-4998 require immediate kernel version upgrades to 4.6 or later, where the vulnerability has been addressed through proper bounds checking implementation. Organizations should implement comprehensive patch management processes to ensure all systems running affected kernel versions receive updates promptly. Additionally, administrators should consider implementing network segmentation and access controls to limit the potential impact of such vulnerabilities within containerized environments. The fix implemented in kernel version 4.6 specifically addresses the improper bounds checking by validating offset values against the actual size of the ruleset blob, preventing out-of-bounds memory access. Security teams should also monitor for potential exploitation attempts through log analysis and implement intrusion detection systems that can identify unusual patterns of setsockopt calls with suspicious offset values. This vulnerability highlights the importance of kernel security hardening and the need for continuous security assessment of core system components that handle user input in privileged contexts.