CVE-2017-18509 in Linux
Summary
by MITRE
An issue was discovered in net/ipv6/ip6mr.c in the Linux kernel before 4.11. By setting a specific socket option, an attacker can control a pointer in kernel land and cause an inet_csk_listen_stop general protection fault, or potentially execute arbitrary code under certain circumstances. The issue can be triggered as root (e.g., inside a default LXC container or with the CAP_NET_ADMIN capability) or after namespace unsharing. This occurs because sk_type and protocol are not checked in the appropriate part of the ip6_mroute_* functions. NOTE: this affects Linux distributions that use 4.9.x longterm kernels.
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Analysis
by VulDB Data Team • 11/23/2023
The vulnerability identified as CVE-2017-18509 represents a critical kernel-level flaw in the Linux IPv6 multicast routing implementation that affects versions prior to 4.11. This issue resides within the net/ipv6/ip6mr.c file and stems from inadequate validation of socket options during multicast routing operations. The flaw allows for potential privilege escalation and arbitrary code execution through a carefully crafted socket option manipulation that manipulates kernel memory pointers. The vulnerability is particularly concerning because it can be exploited by users with minimal privileges, including those with CAP_NET_ADMIN capability or root access within container environments such as default LXC containers. The technical root cause lies in the improper validation of socket type and protocol parameters within the ip6_mroute_* functions, which should have been checked in the appropriate code path to prevent unauthorized pointer manipulation.
The operational impact of this vulnerability extends beyond simple denial of service scenarios, as it can lead to complete system compromise when exploited successfully. An attacker can trigger a general protection fault through the inet_csk_listen_stop function by controlling a kernel pointer, potentially leading to privilege escalation from user-level processes to kernel-level execution. The attack vector becomes particularly dangerous when considering that the vulnerability can be exploited within containerized environments where default LXC containers provide sufficient privileges to manipulate the affected socket options. Additionally, the issue remains exploitable after namespace unsharing, meaning that even if an attacker has already broken out of a restricted namespace, they can still leverage this vulnerability to escalate privileges further. This characteristic makes the vulnerability especially relevant for container security and microservices architectures where namespace isolation is relied upon for security boundaries.
The security implications of CVE-2017-18509 align with CWE-121, which describes heap-based buffer overflow conditions, and more specifically relates to improper validation of input parameters within kernel space. From an ATT&CK framework perspective, this vulnerability maps to privilege escalation techniques and can be categorized under T1068, which involves exploiting legitimate credentials and system access to gain higher privileges. The vulnerability also connects to T1548.001, which covers abuse of privilege escalation techniques through kernel exploits. Organizations using Linux 4.9.x longterm kernels are particularly at risk since these maintained versions were not patched against this specific flaw. The vulnerability's exploitation requires minimal privileges and can be accomplished through standard network programming interfaces, making it accessible to attackers with basic networking knowledge. Remediation efforts should focus on upgrading to Linux kernel versions 4.11 and later, where the socket option validation has been properly implemented to prevent unauthorized pointer manipulation during multicast routing operations.
This vulnerability demonstrates the critical importance of proper input validation in kernel space operations, particularly when dealing with socket options that can affect core networking functionality. The flaw represents a classic case of insufficient parameter checking in kernel drivers, where the absence of proper sk_type and protocol validation creates a pathway for attackers to manipulate kernel memory structures. The fact that this vulnerability affects longterm kernel versions indicates that the security community recognized the severity of the issue and prioritized its remediation in newer kernel releases. Organizations implementing containerized environments or relying on kernel-level networking features should prioritize patching this vulnerability as it represents a significant risk to system integrity and security boundaries. The exploitability of this vulnerability in default container configurations underscores the need for comprehensive security assessments that consider both host and container-level attack surfaces when implementing Linux-based security solutions.