CVE-2012-2744 in Linux
Summary
by MITRE
net/ipv6/netfilter/nf_conntrack_reasm.c in the Linux kernel before 2.6.34, when the nf_conntrack_ipv6 module is enabled, allows remote attackers to cause a denial of service (NULL pointer dereference and system crash) via certain types of fragmented IPv6 packets.
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Analysis
by VulDB Data Team • 03/26/2021
The vulnerability described in CVE-2012-2744 represents a critical NULL pointer dereference flaw within the Linux kernel's IPv6 connection tracking subsystem. This issue specifically affects systems running kernel versions prior to 2.6.34 where the nf_conntrack_ipv6 module is enabled. The vulnerability manifests when the kernel processes certain fragmented IPv6 packets through the netfilter framework, creating a condition where a null pointer reference occurs during packet reassembly operations. The flaw resides in the nf_conntrack_reasm.c file which handles the reassembly of fragmented IPv6 packets within the connection tracking mechanism.
The technical exploitation of this vulnerability occurs through the manipulation of fragmented IPv6 packets that trigger a specific code path in the kernel's network stack. When the kernel encounters malformed or specially crafted fragmented packets, the connection tracking module fails to properly initialize a pointer structure before attempting to dereference it. This results in an immediate system crash or panic, effectively causing a denial of service condition that renders the affected system unavailable to legitimate network traffic. The vulnerability is particularly dangerous because it can be triggered remotely without requiring authentication or special privileges, making it a prime target for network-based denial of service attacks.
From an operational impact perspective, this vulnerability poses significant risks to network infrastructure and services that rely on Linux-based systems running affected kernel versions. Network equipment, servers, and any system processing IPv6 traffic could become unavailable if subjected to this attack, potentially disrupting critical services and causing widespread downtime. The vulnerability affects the core networking functionality of the Linux kernel, meaning that any service dependent on IPv6 connectivity could be impacted. Organizations with IPv6 enabled networks face particular risk, as the attack vector does not require any special access rights and can be executed from any network location capable of sending IPv6 packets.
The mitigation strategies for this vulnerability involve immediate kernel upgrades to versions 2.6.34 or later where the issue has been resolved through proper pointer initialization and validation checks. System administrators should prioritize patching affected systems and verifying that the nf_conntrack_ipv6 module is properly configured or disabled if IPv6 is not required. Network administrators can also implement packet filtering rules to drop suspicious fragmented IPv6 packets at the network boundary, though this approach provides only partial protection. The vulnerability aligns with CWE-476 which describes NULL pointer dereference conditions, and represents a classic example of how improper memory management in kernel space can lead to system instability and denial of service scenarios. From an ATT&CK framework perspective, this vulnerability maps to the T1499.004 technique for network denial of service attacks, where adversaries leverage kernel-level flaws to disrupt system availability.
This vulnerability demonstrates the critical importance of proper input validation and memory management in kernel space operations. The flaw highlights how seemingly minor issues in packet processing logic can have catastrophic effects on system stability and availability. Organizations should maintain comprehensive patch management programs and conduct regular security assessments to identify and remediate similar vulnerabilities before they can be exploited by malicious actors. The incident underscores the necessity of robust kernel security testing and the importance of maintaining up-to-date system configurations to prevent exploitation of known vulnerabilities.