CVE-2001-1194 in Prestige
Summary
by MITRE
Zyxel Prestige 681 and 1600 SDSL Routers allow remote attackers to cause a denial of service via malformed packets with (1) an IP length less than actual packet size, or (2) fragmented packets whose size exceeds 64 kilobytes after reassembly.
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Analysis
by VulDB Data Team • 09/08/2024
The Zyxel Prestige 681 and 1600 SDSL routers present a critical network vulnerability that stems from insufficient input validation in their IP packet processing mechanisms. This vulnerability manifests when the routers encounter malformed network traffic that violates standard Internet Protocol specifications, creating a scenario where legitimate network operations can be disrupted through carefully crafted malicious packets. The flaw exists within the router's network stack implementation, specifically in how it handles IP header validation and packet reassembly processes, making it susceptible to exploitation by remote attackers without requiring any authentication or privileged access.
The technical exploitation occurs through two distinct vectors that leverage fundamental weaknesses in IP protocol handling. The first vector involves sending packets with an IP length field that is smaller than the actual packet payload, causing the router to misinterpret packet boundaries and potentially leading to buffer overflows or memory corruption during packet processing. The second vector exploits fragmented packet handling by sending fragments that, when reassembled, exceed the 64 kilobyte limit specified in standard IP protocol implementations. This second condition triggers a critical failure in the router's reassembly logic, as it fails to properly validate fragment sizes before attempting to reconstruct the original packet. Both attack vectors are classified under CWE-129, Input Validation, and CWE-128, Buffer Overflow, with the specific implementation flaw falling under CWE-20, Improper Input Validation, which aligns with the broader ATT&CK technique T1498, Network Denial of Service.
The operational impact of this vulnerability extends beyond simple service disruption, as it represents a fundamental security weakness that can be exploited to render network infrastructure completely inoperable. When successfully exploited, the denial of service condition affects not only the targeted router but can also potentially impact network connectivity for all devices relying on that router as their primary gateway. The vulnerability's remote nature means that attackers can initiate attacks from anywhere on the internet without requiring physical access or network proximity. The attack requires minimal resources to execute and can be automated, making it particularly dangerous for network administrators who may not immediately detect the service disruption. This vulnerability directly impacts the availability aspect of the CIA triad, specifically targeting the availability of network services and potentially causing cascading failures in network infrastructure that depends on these devices.
Mitigation strategies for this vulnerability must address both immediate protection and long-term architectural improvements. The most effective immediate solution involves implementing network access control lists and packet filtering rules that can identify and block malformed packets before they reach the vulnerable router infrastructure. Network administrators should configure routers to drop packets with invalid IP length fields or oversized fragments, effectively creating a defense in depth approach. Additionally, firmware updates from Zyxel should be applied immediately, as these devices were manufactured in an era when security patches were less commonly provided. The implementation of intrusion detection systems can also help identify exploitation attempts by monitoring for patterns consistent with this vulnerability. Organizations should also consider implementing network segmentation to limit the impact of such attacks, ensuring that a compromised router does not affect the entire network infrastructure. This vulnerability highlights the importance of proper protocol implementation and validation, aligning with industry standards such as those specified in the ISO/IEC 15408 Common Criteria and NIST Special Publication 800-125 for secure network device design and implementation practices.