CVE-2007-1497 in Linux
Summary
by MITRE
nf_conntrack in netfilter in the Linux kernel before 2.6.20.3 does not set nfctinfo during reassembly of fragmented packets, which leaves the default value as IP_CT_ESTABLISHED and might allow remote attackers to bypass certain rulesets using IPv6 fragments.
If you want to get best quality of vulnerability data, you may have to visit VulDB.
Analysis
by VulDB Data Team • 03/15/2021
The vulnerability described in CVE-2007-1497 resides within the netfilter framework of the Linux kernel, specifically in the nf_conntrack module that handles connection tracking for network traffic. This issue affects kernel versions prior to 2.6.20.3 and represents a significant flaw in the handling of IPv6 fragmented packets. The vulnerability stems from the improper initialization of connection tracking information during the packet reassembly process, creating a potential bypass mechanism for firewall rules and security policies.
The technical flaw occurs when the kernel receives fragmented IPv6 packets that require reassembly before processing. During this reassembly process, the nf_conntrack module fails to properly set the nfctinfo field, which is crucial for determining the connection state and tracking information. This field normally indicates the relationship between the packet and its connection, but when left unset, it defaults to IP_CT_ESTABLISHED. This default value can be exploited by attackers who craft specific fragmented packets to manipulate the connection tracking state, effectively bypassing firewall rules that depend on proper connection state detection.
The operational impact of this vulnerability is particularly concerning in network security contexts where stateful packet inspection is relied upon for protection. Attackers can leverage this weakness to establish connections that appear to be legitimate established connections, thereby circumventing firewall rules that should block certain traffic patterns. This allows for potential unauthorized access, data exfiltration, or other malicious activities that would normally be prevented by properly functioning stateful filtering mechanisms. The vulnerability specifically targets IPv6 traffic, which was becoming increasingly prevalent in network environments, making it particularly dangerous for modern network infrastructures.
This vulnerability aligns with CWE-119, which describes weaknesses related to improper initialization of data structures, and can be mapped to ATT&CK technique T1071.004 for application layer protocol usage. The flaw represents a failure in proper state management within the kernel's connection tracking subsystem, creating an exploitable condition where the default connection state can be manipulated. Network administrators and security professionals should consider this vulnerability when implementing IPv6 security policies, as it undermines the fundamental assumptions of stateful firewall operations. The fix involves properly initializing the nfctinfo field during packet reassembly, ensuring that connection tracking information accurately reflects the actual connection state rather than defaulting to established.
Mitigation strategies should include immediate kernel updates to version 2.6.20.3 or later, which contain the necessary patches to properly initialize connection tracking information. Organizations should also implement additional network monitoring to detect anomalous fragmented packet behavior that might indicate exploitation attempts. Network segmentation and redundant security controls should be considered as defensive measures, given that the vulnerability affects core kernel functionality. The issue highlights the importance of thorough testing of security-critical kernel components, particularly those involved in connection tracking and packet reassembly operations.