CVE-2011-1170 in Linux
Summary
by MITRE
net/ipv4/netfilter/arp_tables.c in the IPv4 implementation in the Linux kernel before 2.6.39 does not place the expected \0 character at the end of string data in the values of certain structure members, which allows local users to obtain potentially sensitive information from kernel memory by leveraging the CAP_NET_ADMIN capability to issue a crafted request, and then reading the argument to the resulting modprobe process.
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Analysis
by VulDB Data Team • 11/13/2021
The vulnerability identified as CVE-2011-1170 resides within the Linux kernel's IPv4 netfilter implementation, specifically in the arp_tables.c file that handles arp table operations. This flaw represents a classic information disclosure issue that arises from improper string termination within kernel data structures. The vulnerability affects Linux kernel versions prior to 2.6.39 and demonstrates how seemingly minor implementation details can lead to significant security implications when exploited by privileged local users.
The technical root cause of this vulnerability stems from the failure to properly null-terminate string data within specific structure members of the kernel's arp table handling code. When a local user with CAP_NET_ADMIN capability issues a crafted request to the kernel's netfilter subsystem, the kernel processes this request and subsequently passes arguments to the modprobe process. Due to the missing null terminator character, the string data extends beyond its intended boundaries, causing adjacent kernel memory contents to be inadvertently included in the argument passed to modprobe. This memory leakage occurs because the kernel's string handling functions do not properly enforce null termination, allowing arbitrary kernel memory contents to be exposed through the modprobe interface.
The operational impact of this vulnerability extends beyond simple information disclosure, as it provides attackers with access to potentially sensitive kernel memory contents that could include cryptographic keys, passwords, or other confidential data structures. The exploitation requires local access with CAP_NET_ADMIN capability, which represents a privilege escalation vector that could be leveraged by malicious users who have already gained some level of system access. This capability allows users to manipulate network filter rules, making the attack surface more accessible compared to purely remote vulnerabilities. The vulnerability aligns with CWE-121, which addresses stack-based buffer overflow conditions, and demonstrates how improper string handling can lead to memory disclosure issues.
The attack scenario typically involves a local user with sufficient privileges to make netfilter requests, who then crafts a specific arp table rule that triggers the flawed string handling code path. When the kernel processes this rule and subsequently invokes modprobe with the improperly terminated string, the resulting memory dump contains information that could be valuable for further exploitation attempts. This vulnerability is particularly concerning because it operates at the kernel level, where the memory contents can include sensitive information from other kernel processes or data structures. The flaw also relates to ATT&CK technique T1059.003, which involves the use of command and scripting interpreter to execute commands, as the modprobe invocation provides an indirect path for information extraction.
Mitigation strategies for CVE-2011-1170 primarily involve upgrading to Linux kernel version 2.6.39 or later, where the string termination issue has been properly addressed. System administrators should also implement strict access controls to limit the number of users with CAP_NET_ADMIN capability, as this privilege is not required for normal system operations. Additional defensive measures include monitoring for unusual modprobe invocations and implementing kernel hardening techniques such as stack canaries and kernel address space layout randomization. The vulnerability highlights the importance of proper input validation and string handling in kernel code, emphasizing that even minor implementation oversights can create significant security risks that may be exploited by determined attackers.