CVE-2016-3841 in Android
Summary
by MITRE
The IPv6 stack in the Linux kernel before 4.3.3 mishandles options data, which allows local users to gain privileges or cause a denial of service (use-after-free and system crash) via a crafted sendmsg system call.
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Analysis
by VulDB Data Team • 09/12/2022
The vulnerability identified as CVE-2016-3841 represents a critical flaw in the Linux kernel's IPv6 implementation that affects versions prior to 4.3.3. This issue manifests in the improper handling of options data within the IPv6 stack, creating a pathway for malicious actors to exploit the system through crafted sendmsg system calls. The vulnerability specifically targets the kernel's network subsystem where IPv6 options are processed, exposing a fundamental flaw in memory management and data validation mechanisms. The affected code path involves the kernel's handling of IPv6 extension headers and option processing during network communication operations.
The technical exploitation of this vulnerability occurs through a use-after-free condition that arises when the kernel processes malformed IPv6 options within a sendmsg system call. When an attacker crafts a specific sequence of options data that triggers the kernel's IPv6 processing routines, the system attempts to access memory that has already been freed or deallocated. This memory corruption scenario can be leveraged to execute arbitrary code with elevated privileges or to cause a system crash through a denial of service condition. The vulnerability stems from insufficient validation of option data length and structure, allowing attackers to manipulate the kernel's memory management functions. The flaw is particularly dangerous because it operates at the kernel level where any successful exploitation can result in complete system compromise.
From an operational perspective, this vulnerability poses significant risks to Linux systems that utilize IPv6 networking capabilities. Local users with minimal privileges can exploit this weakness to escalate their privileges to root level access, effectively bypassing standard security controls. The potential for denial of service attacks is equally concerning as system crashes can disrupt critical network services and applications. The vulnerability affects systems running Linux kernel versions 2.6.32 through 4.3.2, making it a widespread concern across numerous production environments. Security researchers have classified this issue as high severity due to its local exploitation requirements and the potential for privilege escalation, which aligns with CWE-416: Use After Free vulnerability pattern. The attack vector requires local access to the system but does not require network connectivity, making it particularly insidious in environments where local user access is not properly restricted.
The mitigation strategy for CVE-2016-3841 centers on upgrading the Linux kernel to version 4.3.3 or later, which contains the necessary patches to address the IPv6 option handling flaw. System administrators should prioritize this update across all affected systems, particularly those running older kernel versions. Additional protective measures include implementing strict access controls to limit local user privileges, monitoring for suspicious network activity patterns, and applying kernel hardening techniques such as stack canaries and address space layout randomization. Organizations should also consider implementing network segmentation to reduce the attack surface and ensure that IPv6 functionality is disabled on systems where it is not required. The vulnerability demonstrates the critical importance of maintaining current kernel versions and highlights the need for comprehensive security testing of core system components. This issue also correlates with ATT&CK technique T1068: Exploitation for Privilege Escalation, where attackers leverage system vulnerabilities to gain elevated privileges, and T1499: Endpoint Denial of Service, which encompasses methods of causing system disruption through kernel-level flaws. Regular security audits and vulnerability assessments should include checks for outdated kernel versions to prevent exploitation of similar vulnerabilities in the future.