CVE-2002-0046 in Linux
Summary
by MITRE
Linux kernel, and possibly other operating systems, allows remote attackers to read portions of memory via a series of fragmented ICMP packets that generate an ICMP TTL Exceeded response, which includes portions of the memory in the response packet.
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Analysis
by VulDB Data Team • 05/25/2019
This vulnerability represents a classic information disclosure flaw in network protocol implementations that affects the linux kernel and potentially other operating systems. The issue stems from how the kernel handles fragmented internet control message protocol packets, specifically when processing ttl exceeded responses. When an attacker sends a series of carefully crafted fragmented icmp packets, the kernel generates icmp ttl exceeded responses that inadvertently include portions of the kernel's memory in the response packet structure. This occurs because the kernel does not properly sanitize the memory contents before including them in the icmp response, creating a scenario where sensitive data from kernel memory space can be extracted by remote attackers.
The technical exploitation mechanism relies on the kernel's handling of fragmented packets and its response generation process. When a packet arrives with a ttl value of zero, the kernel sends back an icmp ttl exceeded message to inform the sender. However, when dealing with fragmented packets, the kernel's response generation logic fails to properly clear or validate the memory contents that are included in the icmp response. This memory leakage can potentially expose kernel data structures, stack contents, or other sensitive information that was present in the memory regions used for processing the fragmented packets. The vulnerability is particularly concerning because it operates at the network protocol level and can be exploited remotely without requiring authentication or local access to the system.
The operational impact of this vulnerability extends beyond simple information disclosure, as it can provide attackers with valuable insights into the kernel's memory layout and internal state. This information can be leveraged to aid in more sophisticated attacks such as kernel exploitation, privilege escalation, or targeted attacks against specific kernel components. The memory contents that are leaked can include kernel data structures, function pointers, stack contents, and other potentially sensitive information that could be used to craft more effective attacks. This vulnerability is categorized under the common weakness enumeration as a weakness related to information exposure through improper handling of memory contents in network protocols, specifically falling under the category of information disclosure vulnerabilities that can be exploited through network-based attacks.
Mitigation strategies for this vulnerability primarily focus on kernel-level fixes and network configuration approaches. The most effective solution involves implementing proper memory sanitization in the icmp response generation code, ensuring that no kernel memory contents are inadvertently included in icmp ttl exceeded responses. Network administrators should also consider implementing firewall rules that limit icmp traffic or filter out suspicious fragmented packet patterns. Additionally, keeping kernel versions up to date with the latest security patches is crucial as this vulnerability was addressed in subsequent kernel releases. The mitigation approach aligns with the attack technique of information gathering and reconnaissance, where attackers typically seek to understand system internals before launching more targeted attacks. Organizations should also consider implementing network monitoring to detect unusual icmp traffic patterns that might indicate exploitation attempts, as this vulnerability operates at a fundamental network protocol level that can be difficult to detect through traditional application-level monitoring systems.