CVE-2001-0518 in Oracle
Summary
by MITRE
Oracle listener before Oracle 9i allows attackers to cause a denial of service by repeatedly sending the first portion of a fragmented Oracle command without sending the remainder of the command, which causes the listener to hang.
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Analysis
by VulDB Data Team • 04/08/2019
The vulnerability identified as CVE-2001-0518 represents a classic denial of service flaw in Oracle database listener software prior to Oracle 9i versions. This weakness exploits the listener's handling of fragmented network commands, specifically targeting how the system processes incomplete communication sequences. The Oracle listener serves as a critical component that manages incoming connections and forwards requests to the appropriate database processes, making it a prime target for attackers seeking to disrupt database services. The flaw manifests when an attacker sends the initial portion of a fragmented Oracle command while deliberately omitting the subsequent fragments, creating a state where the listener remains in a waiting condition indefinitely.
The technical implementation of this vulnerability stems from inadequate validation and timeout mechanisms within the Oracle listener's protocol handling. When the listener receives the first segment of a command, it typically waits for additional fragments to complete the full command structure. However, the vulnerable implementation fails to properly time out or detect when these remaining fragments will never arrive, resulting in the listener process becoming unresponsive. This behavior creates a resource exhaustion condition where the listener thread remains occupied indefinitely, preventing it from processing legitimate incoming requests. The flaw operates at the network protocol level and affects the listener's ability to maintain proper connection handling and resource allocation.
From an operational perspective, this vulnerability presents significant risks to database availability and business continuity. An attacker requiring minimal network access can effectively render database services unavailable by sending a single malformed fragmented command, causing the listener to hang and preventing legitimate database connections. The impact extends beyond simple service disruption as the hanging listener process consumes system resources and can potentially affect other database operations. Organizations relying on Oracle databases for critical business applications face substantial risk of operational downtime, especially in environments where database availability is paramount. The vulnerability's exploitability is particularly concerning because it requires minimal technical expertise and network access, making it attractive to attackers seeking to cause disruption without sophisticated attack capabilities.
The vulnerability aligns with CWE-400, which classifies this as a weakness related to resource management and improper handling of incomplete data sequences. It also corresponds to ATT&CK technique T1499, specifically targeting the denial of service aspect through resource exhaustion. Mitigation strategies should include immediate patching of Oracle listener software to Oracle 9i or later versions where the vulnerability has been addressed. Network-level protections such as implementing connection rate limiting and monitoring for unusual fragmented command patterns can provide additional defense layers. System administrators should configure appropriate timeout values for listener processes and implement proper resource monitoring to detect hanging processes. Organizations should also consider network segmentation and access controls to limit exposure of Oracle listener services to untrusted networks, reducing the attack surface for such vulnerabilities. Regular security assessments and vulnerability scanning should be conducted to identify any remaining instances of vulnerable listener versions within the infrastructure.