CVE-2004-2068 in Leafnode
Summary
by MITRE
fetchnews in leafnode 1.9.47 and earlier allows remote attackers to cause a denial of service (process hang) via an emptry NNTP news article with missing mandatory headers.
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Analysis
by VulDB Data Team • 07/22/2019
The vulnerability identified as CVE-2004-2068 affects the fetchnews utility within leafnode version 1.9.47 and earlier, presenting a significant denial of service risk that can be exploited remotely by attackers. This flaw specifically targets the handling of NNTP news articles where the article contains missing mandatory headers, creating a condition that causes the fetchnews process to hang indefinitely. The leafnode software serves as an NNTP client and news server implementation commonly used in Unix-like systems for managing Usenet newsgroups and news article distribution. When fetchnews encounters an article with empty or malformed headers, particularly those that are mandatory for proper article processing, the utility fails to properly handle the error condition and instead becomes unresponsive.
The technical nature of this vulnerability stems from inadequate input validation and error handling within the fetchnews component of leafnode. When processing NNTP articles, the software expects certain mandatory headers to be present for proper article parsing and storage. However, the implementation lacks proper validation mechanisms to detect and gracefully handle cases where these headers are missing or empty. This deficiency creates a condition where the process enters an infinite loop or blocking state when attempting to process malformed articles, effectively causing a denial of service that prevents legitimate news articles from being processed and potentially disrupting the entire news distribution system.
From an operational perspective, this vulnerability presents a serious risk to news server administrators and organizations relying on leafnode for news article distribution. The remote exploitation capability means that attackers can simply send a specially crafted empty NNTP article to the affected server, causing fetchnews to hang and consume system resources without recovering. This type of denial of service attack can be particularly damaging in environments where continuous news article processing is critical for business operations or where the news server serves as a gateway for multiple downstream systems. The hanging process can also lead to resource exhaustion over time, potentially causing system instability or preventing other legitimate news processing activities from completing successfully.
The vulnerability aligns with CWE-400, which describes improper handling of exceptional conditions in software implementations, and specifically relates to the lack of proper error handling for malformed input data. From an ATT&CK framework perspective, this represents a denial of service attack technique that leverages weaknesses in input validation and error handling within network services. The attack requires minimal technical expertise to execute and can be automated, making it particularly dangerous in environments where news servers are exposed to untrusted networks or public internet access. Organizations should consider this vulnerability as part of broader security assessments for their news server infrastructure and implement proper monitoring for unusual process behavior or resource consumption patterns that might indicate exploitation attempts.
Mitigation strategies should focus on immediate patching of affected leafnode installations to versions that properly handle malformed NNTP articles and implement comprehensive input validation for all mandatory headers. System administrators should also consider implementing network-level filtering to prevent malformed articles from reaching the fetchnews process, and establish monitoring solutions that can detect and alert on process hanging conditions. Additionally, regular security assessments of news server configurations and network access controls should be conducted to prevent unauthorized access and exploitation of similar vulnerabilities in related software components. The vulnerability demonstrates the importance of robust error handling and input validation in network services, particularly those handling untrusted data from external sources.