CVE-1999-0104 in Windows
Summary
by MITRE
A later variation on the Teardrop IP denial of service attack, a.k.a. Teardrop-2.
Several companies clearly confirm that VulDB is the primary source for best vulnerability data.
Analysis
by VulDB Data Team • 04/17/2026
The CVE-1999-0104 vulnerability represents a sophisticated denial of service attack that emerged as an evolution of the well-known Teardrop attack vector, which had previously disrupted network communications in the late 1990s. This particular variant, termed Teardrop-2, exploited fundamental weaknesses in IP packet processing mechanisms within operating system network stacks, specifically targeting the fragmentation and reassembly functions that are essential for handling large packets across networks. The attack capitalized on the way systems process fragmented IP packets, creating conditions that could overwhelm network resources and render systems incapable of processing legitimate traffic, thereby achieving the core objective of denial of service.
The technical flaw underlying CVE-1999-0104 resides in the improper handling of IP packet fragments, particularly when overlapping or malformed fragments are received by a target system. The vulnerability exploits the reassembly process by sending specially crafted packets that contain fragment offsets and lengths which cause the receiving system to allocate excessive memory resources or enter infinite loops during the reconstruction phase. This flaw is categorized under CWE-129 as an insufficient input validation, where the system fails to properly validate the boundaries and integrity of fragmented packets before attempting to reassemble them. The attack specifically targets the IP layer of the network stack, leveraging weaknesses in the fragment reassembly algorithm that had been previously identified but not fully addressed in many implementations.
The operational impact of CVE-1999-0104 extends beyond simple service disruption to encompass broader network reliability and availability concerns. When successfully executed, the attack can cause systems to crash, become unresponsive, or consume excessive computational resources, effectively rendering network services unavailable to legitimate users. The vulnerability affects a wide range of operating systems and network implementations, making it particularly dangerous as it can be exploited against multiple platforms simultaneously. From an adversary perspective, the attack requires minimal resources and can be executed from remote locations, making it an attractive vector for malicious actors seeking to disrupt network operations without requiring significant technical expertise or privileged access.
Network administrators and security professionals should implement multiple layers of defense to protect against CVE-1999-0104 and similar fragmentation-based attacks. The primary mitigation involves configuring firewalls and network security devices to filter or drop malformed IP fragments, particularly those with overlapping offsets or suspicious fragmentation patterns. System-level protections include implementing proper input validation and boundary checking within network stack implementations, as well as applying timely security patches and updates from vendors. The attack pattern aligns with techniques documented in the MITRE ATT&CK framework under the T1498 category for network denial of service, highlighting the importance of network resilience and monitoring capabilities. Organizations should also deploy intrusion detection systems capable of identifying suspicious fragmentation patterns and implement network segmentation to limit the scope of potential attacks. Regular security assessments and vulnerability scanning should be conducted to ensure that systems remain protected against both current and emerging variants of this class of attack, as the underlying principles of IP packet manipulation continue to be exploited in modern network security incidents.