CVE-2016-9919 in Linux
Summary
by MITRE • 01/25/2023
The icmp6_send function in net/ipv6/icmp.c in the Linux kernel through 4.8.12 omits a certain check of the dst data structure, which allows remote attackers to cause a denial of service (panic) via a fragmented IPv6 packet.
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Analysis
by VulDB Data Team • 01/25/2023
The vulnerability identified as CVE-2016-9919 represents a critical flaw in the Linux kernel's handling of IPv6 internet control message protocol packets, specifically within the icmp6_send function located in net/ipv6/icmp.c. This issue affects Linux kernel versions through 4.8.12 and demonstrates a fundamental failure in the kernel's packet processing logic that can be exploited by remote attackers to trigger system crashes. The vulnerability stems from an incomplete validation of the destination data structure during ICMPv6 packet transmission, creating a path for malicious actors to craft specially crafted fragmented IPv6 packets that can cause the kernel to panic and subsequently crash the entire system.
The technical nature of this vulnerability aligns with CWE-125, which describes an out-of-bounds read condition that can occur when a program accesses memory beyond the boundaries of a buffer or data structure. In this case, the missing validation of the dst data structure during ICMPv6 packet processing creates a scenario where the kernel fails to properly verify the integrity of the destination information before attempting to process fragmented packets. When a remote attacker sends a crafted fragmented IPv6 packet, the kernel's icmp6_send function processes the packet without the necessary validation checks, leading to an invalid memory access that results in a kernel panic. This panic occurs because the kernel attempts to dereference memory locations that are either uninitialized or contain invalid data, causing the system to become unresponsive and requiring manual intervention to restore normal operation.
The operational impact of CVE-2016-9919 extends beyond simple denial of service, as it represents a potential vector for more sophisticated attacks that could be leveraged in combination with other vulnerabilities. The vulnerability can be exploited remotely without requiring any authentication or privileged access, making it particularly dangerous in networked environments where IPv6 traffic is present. Systems running affected kernel versions are vulnerable to this attack regardless of their network configuration or firewall settings, as the exploit targets the kernel's core packet processing mechanisms. This vulnerability particularly affects servers, network infrastructure devices, and any system that processes IPv6 traffic, including routers, switches, and network security appliances that may be operating in dual-stack mode or IPv6-only environments.
Mitigation strategies for CVE-2016-9919 should prioritize immediate kernel updates to versions that contain the necessary patches addressing the missing validation in the icmp6_send function. Organizations should implement network segmentation and access controls to limit exposure to potentially malicious IPv6 traffic, while also monitoring for unusual patterns in IPv6 packet processing that might indicate exploitation attempts. The ATT&CK framework categorizes this vulnerability under the T1499.004 technique for Network Denial of Service, where adversaries leverage system vulnerabilities to exhaust resources or cause system crashes. Security teams should also consider implementing intrusion detection systems with signature-based detection for known patterns of fragmented IPv6 packets that could be used to exploit this vulnerability, while maintaining comprehensive logging of IPv6 traffic for forensic analysis. Additionally, network administrators should review and update their incident response procedures to account for kernel-level panics and ensure rapid recovery capabilities are in place to minimize downtime and service disruption.