CVE-2008-3530 in FreeBSD
Summary
by MITRE
sys/netinet6/icmp6.c in the kernel in FreeBSD 6.3 through 7.1, NetBSD 3.0 through 4.0, and possibly other operating systems does not properly check the proposed new MTU in an ICMPv6 Packet Too Big Message, which allows remote attackers to cause a denial of service (panic) via a crafted Packet Too Big Message.
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Analysis
by VulDB Data Team • 05/27/2025
The vulnerability described in CVE-2008-3530 represents a critical flaw in the implementation of ICMPv6 packet processing within several Unix-like operating systems including FreeBSD versions 6.3 through 7.1 and NetBSD versions 3.0 through 4.0. This issue resides in the kernel-level component responsible for handling IPv6 communication, specifically within the icmp6.c file that manages ICMPv6 packet processing. The flaw manifests when the system receives a crafted ICMPv6 Packet Too Big message, which is a standard mechanism used by network devices to inform senders that their packets exceed the maximum transmission unit of a network path. The vulnerability stems from insufficient validation of the proposed new MTU value contained within these messages, creating a potential pathway for malicious actors to exploit the system's network stack.
The technical implementation of this vulnerability involves a failure in input validation within the kernel's ICMPv6 processing logic. When an ICMPv6 Packet Too Big message is received, the system should verify that the proposed MTU value is reasonable and within acceptable network parameters. However, the affected systems do not properly validate this value, allowing an attacker to craft a message with an arbitrarily large or malformed MTU value. This lack of validation leads to a kernel panic when the system attempts to process the invalid MTU value, resulting in a complete system crash and denial of service condition. The vulnerability specifically affects the kernel's memory management and routing logic, as the system attempts to adjust network parameters based on the malicious MTU value without proper bounds checking.
The operational impact of this vulnerability is severe and directly affects system availability within networked environments. A remote attacker capable of sending crafted ICMPv6 packets to a vulnerable system can trigger a system panic that results in immediate denial of service. This means that network services hosted on affected systems become unavailable to legitimate users, potentially causing significant disruption to network operations. The vulnerability is particularly dangerous because it requires no authentication or special privileges to exploit, making it accessible to any remote attacker who can send ICMPv6 traffic to the target system. The impact extends beyond individual systems to potentially affect network infrastructure, as multiple vulnerable hosts could be targeted simultaneously to create cascading denial of service conditions. From an operational security perspective, this vulnerability represents a critical weakness in the network stack implementation that could be leveraged in coordinated attacks against network availability.
Mitigation strategies for this vulnerability focus on both immediate patching and network-level protections. The primary solution involves applying vendor-specific patches that implement proper MTU value validation within the ICMPv6 processing code. FreeBSD users should upgrade to versions 7.2 or later, while NetBSD users should update to versions 4.0.1 or later where the vulnerability has been addressed through enhanced input validation mechanisms. Network administrators should also consider implementing firewall rules that filter or drop ICMPv6 Packet Too Big messages at network boundaries, though this approach may impact legitimate network operations. The vulnerability aligns with CWE-129, which addresses improper validation of input boundaries, and could be categorized under ATT&CK technique T1499.1 for network denial of service attacks. Organizations should also implement monitoring for unusual ICMPv6 traffic patterns that might indicate exploitation attempts, as well as maintain updated network security baselines that include proper kernel version management and regular security assessments to prevent similar vulnerabilities from being exploited in other system components.