CVE-2011-1172 in Linux
Summary
by MITRE
net/ipv6/netfilter/ip6_tables.c in the IPv6 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 described in CVE-2011-1172 resides within the IPv6 netfilter implementation of the Linux kernel, specifically in the ip6_tables.c file. This flaw affects kernel versions prior to 2.6.39 and represents a classic case of information disclosure through improper string handling in kernel space. The vulnerability manifests when certain structure members containing string data fail to properly terminate their values with the expected null character, creating a condition where adjacent memory contents may be exposed to user-space processes.
The technical exploitation of this vulnerability requires a local attacker possessing the CAP_NET_ADMIN capability, which grants network administration privileges within the Linux security model. This capability is typically held by processes running with elevated privileges or by users who have been granted specific network administration permissions. When an attacker issues a crafted request to the netfilter subsystem, the kernel processes this request and subsequently passes arguments to the modprobe process. Due to the improper string termination in kernel memory structures, the modprobe process receives not only the intended argument but also adjacent kernel memory contents that happen to be interpreted as string data.
The operational impact of this vulnerability extends beyond simple information disclosure, as it can potentially expose sensitive kernel memory contents to local attackers. These contents may include cryptographic keys, passwords, system configuration data, or other confidential information that could be leveraged in subsequent attacks. The vulnerability creates a pathway for privilege escalation or information gathering that could be particularly damaging in environments where kernel memory contains sensitive data. The fact that this requires the CAP_NET_ADMIN capability limits its exposure somewhat, but it still represents a significant security risk in multi-tenant or privileged environments where such capabilities might be granted to less trusted processes.
This vulnerability aligns with CWE-122, which describes improper restriction of operations within a limited context, and specifically relates to improper string termination in kernel memory structures. The ATT&CK framework would categorize this under privilege escalation techniques, specifically T1068, which involves exploiting weaknesses in the system to gain higher privileges. The vulnerability also demonstrates characteristics of T1552, which involves data manipulation and access to sensitive information, and T1059, which involves command and scripting interpreters to execute malicious code. The exploitation path requires careful crafting of netfilter requests that trigger the kernel memory corruption, making it a sophisticated attack vector that could be used in advanced persistent threat scenarios.
The recommended mitigations for this vulnerability include immediate patching of the Linux kernel to version 2.6.39 or later, where the string termination issue has been corrected. System administrators should also implement proper capability management to limit the distribution of CAP_NET_ADMIN privileges to only those processes that absolutely require them. Additional monitoring should be implemented to detect anomalous netfilter activity that might indicate exploitation attempts. The vulnerability highlights the importance of proper memory management practices in kernel space, particularly around string handling and buffer management, and serves as a reminder of the critical security implications that can arise from seemingly minor implementation flaws in core system components. Organizations should conduct thorough vulnerability assessments to identify systems running affected kernel versions and ensure proper patch management procedures are in place to prevent exploitation of similar vulnerabilities.