CVE-2015-8787 in Linux
Summary
by MITRE • 01/25/2023
The nf_nat_redirect_ipv4 function in net/netfilter/nf_nat_redirect.c in the Linux kernel before 4.4 allows remote attackers to cause a denial of service (NULL pointer dereference and system crash) or possibly have unspecified other impact by sending certain IPv4 packets to an incompletely configured interface, a related issue to CVE-2003-1604.
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Analysis
by VulDB Data Team • 01/25/2023
The vulnerability identified as CVE-2015-8787 resides within the Linux kernel's network filtering subsystem, specifically in the nf_nat_redirect_ipv4 function located at net/netfilter/nf_nat_redirect.c. This flaw represents a critical NULL pointer dereference issue that affects Linux kernel versions prior to 4.4, creating a significant security risk for systems utilizing network address translation functionality. The vulnerability manifests when remote attackers exploit improperly configured network interfaces, particularly those that are incompletely set up or in transitional states during network configuration. The issue is classified as a denial of service condition that can result in complete system crashes, making it particularly dangerous for network infrastructure devices and servers that rely on NAT functionality for traffic management.
The technical root cause of this vulnerability stems from inadequate input validation within the network address translation redirect mechanism. When the nf_nat_redirect_ipv4 function processes certain IPv4 packets, it fails to properly validate the state of network interfaces before attempting to access pointers associated with those interfaces. This leads to a NULL pointer dereference when the function attempts to access memory locations that have not been properly initialized or allocated. The vulnerability is particularly insidious because it can be triggered through seemingly benign network traffic, making it difficult to detect and prevent through standard network monitoring. The flaw operates at the kernel level, bypassing user-space protections and directly impacting the operating system's stability and availability. This type of vulnerability aligns with CWE-476, which specifically addresses NULL pointer dereference conditions, and represents a classic example of inadequate error handling in kernel-space code.
The operational impact of CVE-2015-8787 extends beyond simple system crashes to potentially compromise entire network infrastructures. Systems running affected kernel versions that utilize NAT functionality become vulnerable to remote exploitation, allowing attackers to disrupt network services without requiring elevated privileges. The vulnerability's similarity to CVE-2003-1604 indicates a persistent pattern in kernel network filtering code where interface state management remains inadequate. Network administrators may experience unexpected downtime, service interruptions, and potential data loss when systems become unresponsive due to these crashes. The vulnerability particularly affects routers, firewalls, and network appliances that heavily utilize NAT for traffic management, making it a critical concern for enterprise network security. Additionally, the potential for unspecified other impacts suggests that attackers might be able to leverage this vulnerability for more advanced exploitation techniques beyond simple denial of service.
Mitigation strategies for CVE-2015-8787 primarily focus on kernel version upgrades to 4.4 or later, which contain the necessary patches to address the NULL pointer dereference issue. System administrators should prioritize updating their kernel versions as a critical security measure, particularly in environments where NAT functionality is actively used. Network segmentation and firewall rules can provide temporary protection by limiting exposure to potentially malicious IPv4 traffic, though these measures do not address the underlying vulnerability. Monitoring for unusual network traffic patterns and system crashes can help detect exploitation attempts, while implementing proper network interface configuration procedures can reduce the likelihood of triggering the vulnerability. Organizations should also consider implementing intrusion detection systems that can identify patterns consistent with this vulnerability's exploitation. The ATT&CK framework categorizes this type of vulnerability under privilege escalation and denial of service techniques, making it a significant concern for security operations centers that must maintain system availability and network integrity. Regular security audits and vulnerability assessments should include checks for this specific kernel vulnerability to ensure comprehensive protection against network-based attacks.