CVE-2011-2699 in Solaris
Summary
by MITRE
The IPv6 implementation in the Linux kernel before 3.1 does not generate Fragment Identification values separately for each destination, which makes it easier for remote attackers to cause a denial of service (disrupted networking) by predicting these values and sending crafted packets.
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Analysis
by VulDB Data Team • 03/26/2021
The vulnerability described in CVE-2011-2699 represents a critical flaw in the Linux kernel's IPv6 implementation that affects systems running versions prior to 3.1. This issue stems from the improper generation of Fragment Identification values within the IPv6 fragmentation process, creating predictable patterns that adversaries can exploit to disrupt network communications. The flaw exists in the kernel's handling of IPv6 packet fragmentation where the system fails to maintain unique identification values for each destination address, violating fundamental security principles for network protocol implementation.
The technical root cause of this vulnerability lies in the kernel's failure to properly randomize or generate unique Fragment Identification values for IPv6 packets destined for different addresses. In standard IPv6 fragmentation, each fragment requires a unique identification value to ensure proper reassembly at the destination. When this value is predictable or reused across multiple destinations, it creates opportunities for attackers to manipulate the fragmentation process. This weakness specifically affects the IPv6 fragmentation mechanism where the kernel generates these values without sufficient entropy or destination-specific uniqueness, making it susceptible to prediction attacks.
The operational impact of CVE-2011-2699 enables remote attackers to execute denial of service attacks by leveraging the predictable nature of Fragment Identification values. Attackers can craft specially designed packets that exploit this predictability to disrupt network connectivity, causing fragmented packets to be incorrectly assembled or rejected by the target system. This vulnerability particularly affects network infrastructure and servers that handle IPv6 traffic, potentially leading to widespread service disruption and network instability. The attack vector requires minimal privileges and can be executed remotely, making it especially dangerous in environments where IPv6 is deployed alongside IPv4.
This vulnerability maps directly to CWE-330, which addresses the use of weak random number generators or predictable values in security-critical contexts. The flaw also aligns with ATT&CK technique T1498, which covers network denial of service attacks, and T1562.001, covering evasion through network disruption. The improper implementation of cryptographic randomness in network protocol handling demonstrates a failure to meet security standards for protocol design and implementation. Organizations affected by this vulnerability should prioritize immediate patching of their Linux kernel versions to 3.1 or later, as this represents the first version that properly addresses the Fragment Identification generation issue.
Mitigation strategies for CVE-2011-2699 primarily focus on kernel version updates and network-level protections. System administrators should implement immediate kernel upgrades to versions 3.1 or higher where the vulnerability has been resolved through proper Fragment Identification value generation. Additional defensive measures include implementing network monitoring to detect anomalous fragmentation patterns and configuring firewalls to limit IPv6 fragmentation traffic. The fix introduced in kernel version 3.1 ensures that each destination receives unique Fragment Identification values, eliminating the predictability that made this attack vector viable. Organizations should also conduct comprehensive security assessments to identify systems running vulnerable kernel versions and implement robust patch management procedures to prevent similar issues in the future.