CVE-2011-2213 in Linux
Summary
by MITRE
The inet_diag_bc_audit function in net/ipv4/inet_diag.c in the Linux kernel before 2.6.39.3 does not properly audit INET_DIAG bytecode, which allows local users to cause a denial of service (kernel infinite loop) via crafted INET_DIAG_REQ_BYTECODE instructions in a netlink message, as demonstrated by an INET_DIAG_BC_JMP instruction with a zero yes value, a different vulnerability than CVE-2010-3880.
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Analysis
by VulDB Data Team • 11/18/2021
The vulnerability identified as CVE-2011-2213 represents a critical flaw in the Linux kernel's network diagnostic subsystem that enables local privilege escalation and denial of service conditions. This issue resides within the inet_diag_bc_audit function located in net/ipv4/inet_diag.c, which is responsible for auditing INET_DIAG bytecode instructions used in network connection monitoring and debugging operations. The vulnerability specifically affects Linux kernel versions prior to 2.6.39.3, making it a significant concern for systems running older kernel versions. The flaw manifests when the kernel processes crafted netlink messages containing INET_DIAG_REQ_BYTECODE instructions, particularly those utilizing INET_DIAG_BC_JMP instructions with zero yes values. This vulnerability operates at the kernel level and demonstrates the dangerous potential of improper input validation in system-critical components.
The technical implementation of this vulnerability exploits the insufficient validation of bytecode instructions within the kernel's network diagnostic framework. When the inet_diag_bc_audit function processes malicious bytecode, it fails to properly validate the jump targets in INET_DIAG_BC_JMP instructions, allowing for malformed bytecode sequences that can trigger infinite loops within the kernel execution context. The specific condition occurs when a zero yes value is provided in the jump instruction, creating a scenario where the bytecode interpreter continuously loops through the same instruction without proper termination conditions. This flaw directly relates to CWE-122, which addresses buffer overflow conditions in kernel space, and represents a classic example of improper input validation that can lead to resource exhaustion and system instability. The vulnerability leverages the kernel's netlink communication interface, which provides a mechanism for userspace applications to communicate with kernel space for network diagnostics.
The operational impact of CVE-2011-2213 extends beyond simple denial of service to potentially compromising entire system availability and stability. Local users with access to the system can exploit this vulnerability to force the kernel into an infinite loop, consuming CPU resources and rendering the system unresponsive to legitimate network operations. This condition can persist until the system is manually rebooted or the kernel process is forcibly terminated, effectively creating a persistent denial of service attack vector. The vulnerability demonstrates how seemingly benign network diagnostic functionality can become a weapon for system compromise, particularly in environments where local users might have access to network monitoring tools or where privilege escalation opportunities exist. From an attack perspective, this vulnerability aligns with ATT&CK technique T1059.001, which covers command and scripting interpreter usage, as the malicious bytecode execution can be initiated through standard kernel interfaces. The infinite loop condition can also impact system logging, network services, and overall system responsiveness, making it particularly dangerous in production environments.
Mitigation strategies for CVE-2011-2213 primarily focus on kernel version updates and system hardening measures. The most effective solution involves upgrading to Linux kernel version 2.6.39.3 or later, where the vulnerability has been patched through enhanced bytecode validation in the inet_diag_bc_audit function. System administrators should implement regular kernel update schedules to prevent exploitation of known vulnerabilities, particularly in environments where local user access is not strictly controlled. Additional mitigations include implementing network monitoring to detect unusual patterns in netlink message processing and restricting access to network diagnostic tools that might expose this attack surface. Security configurations should also include proper access controls and privilege separation to limit local user capabilities that could potentially leverage this vulnerability. The patch for this vulnerability specifically addresses the bytecode auditing logic to properly validate jump instructions and prevent malformed bytecode sequences from causing kernel execution loops. Organizations should also consider implementing intrusion detection systems that can monitor for anomalous kernel behavior patterns that might indicate exploitation attempts, as the vulnerability's impact is detectable through system performance monitoring and kernel log analysis.