CVE-2005-0036 in 3800
Summary
by MITRE
The DNS implementation in DeleGate 8.10.2 and earlier allows remote attackers to cause a denial of service via a compressed DNS packet with a label length byte with an incorrect offset, which could trigger an infinite loop.
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Analysis
by VulDB Data Team • 03/11/2021
The vulnerability identified as CVE-2005-0036 represents a critical flaw in the DNS implementation of DeleGate version 8.10.2 and earlier systems. This issue manifests as a denial of service condition that can be triggered remotely through the manipulation of DNS packet structures. The vulnerability specifically targets the decompression mechanism within the DNS processing code, where improper handling of label length bytes leads to system instability.
The technical root cause of this vulnerability lies in the improper validation of compressed DNS packet structures during the decompression process. When a maliciously crafted DNS packet contains a label length byte with an incorrect offset, the DeleGate server enters an infinite loop while attempting to process the malformed data. This occurs because the decompression algorithm fails to properly validate the pointer references within the DNS compressed format, causing the parser to repeatedly follow invalid pointers and never reach a termination condition. The vulnerability directly maps to CWE-121, which addresses buffer overflow conditions in the context of memory management and pointer handling.
From an operational perspective, this vulnerability presents a significant risk to network infrastructure services that rely on DeleGate for DNS resolution and caching operations. Attackers can exploit this flaw by sending carefully crafted DNS queries to the affected server, causing it to consume excessive CPU resources and eventually become unresponsive. The infinite loop nature of the vulnerability means that once triggered, the service remains unavailable until manually restarted, potentially disrupting critical network services and user access. This type of attack aligns with ATT&CK technique T1498, which covers network denial of service attacks that compromise system availability.
The impact of this vulnerability extends beyond simple service disruption as it can be leveraged as part of broader attack campaigns targeting network infrastructure. Organizations using DeleGate versions prior to 8.10.3 should consider this vulnerability as a high-priority remediation target, particularly in environments where DNS services are critical to business operations. The vulnerability demonstrates the importance of proper input validation in network protocol implementations and highlights the need for robust error handling in parsing routines.
Mitigation strategies for this vulnerability include immediate patching to DeleGate version 8.10.3 or later, which contains the necessary fixes for proper DNS packet validation. Network administrators should also implement monitoring for unusual DNS traffic patterns that might indicate exploitation attempts. Additionally, deploying network segmentation and access controls can limit the potential impact of such attacks, while implementing rate limiting on DNS query processing can help reduce the effectiveness of automated exploitation attempts. The fix addresses the core issue by implementing proper bounds checking and validation of pointer offsets within compressed DNS records, preventing the infinite loop condition that previously occurred when encountering malformed data structures.