CVE-2009-2625 in JRE
Summary
by MITRE
XMLScanner.java in Apache Xerces2 Java, as used in Sun Java Runtime Environment (JRE) in JDK and JRE 6 before Update 15 and JDK and JRE 5.0 before Update 20, and in other products, allows remote attackers to cause a denial of service (infinite loop and application hang) via malformed XML input, as demonstrated by the Codenomicon XML fuzzing framework.
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Analysis
by VulDB Data Team • 02/02/2025
The vulnerability identified as CVE-2009-2625 represents a critical denial of service flaw within Apache Xerces2 Java's XMLScanner.java component, which was widely distributed across multiple Java runtime environments including Sun's JRE and JDK versions. This vulnerability specifically affects systems running JDK and JRE 6 before Update 15 and JDK and JRE 5.0 before Update 20, making it a significant concern for organizations maintaining legacy Java deployments. The flaw manifests when the XML parser encounters malformed XML input that triggers an infinite loop within the scanning process, ultimately causing the application to hang and become unresponsive to legitimate requests.
The technical mechanism behind this vulnerability involves the XMLScanner's inadequate handling of malformed input sequences that cause the parser to enter an infinite loop during the processing of XML documents. When the parser encounters specific malformed XML structures, particularly those designed to exploit parsing weaknesses, the scanning algorithm fails to properly terminate its processing loop, resulting in continuous CPU consumption and application hang conditions. This behavior aligns with CWE-835, which describes the weakness of an infinite loop in software implementations. The vulnerability was demonstrated through the Codenomicon XML fuzzing framework, indicating that it could be reliably exploited by attackers using automated tools designed to generate malformed XML content that specifically targets parsing vulnerabilities in XML processors.
The operational impact of this vulnerability extends beyond simple service disruption, as it can be leveraged by attackers to perform denial of service attacks against applications that rely on XML processing capabilities. Systems utilizing affected Java runtime environments become vulnerable to attacks that can cause complete application unavailability, potentially affecting web applications, enterprise systems, and any software that processes XML data from external sources. The vulnerability's presence in widely deployed Java components means that organizations across various industries could be impacted, particularly those with legacy systems that have not received the necessary security updates. This makes the vulnerability particularly dangerous as it can affect a broad spectrum of applications and services that depend on standard XML parsing functionality.
Organizations should prioritize immediate patching of affected systems by applying the relevant security updates from Oracle for JDK and JRE versions, specifically targeting the updates that address this XML parsing vulnerability. The mitigation strategy should include comprehensive testing of patched environments to ensure that the fix does not introduce regressions in existing XML processing functionality. Additionally, implementing input validation measures at application boundaries can provide defense-in-depth protection against malformed XML content, though this approach should not be considered a substitute for proper patching. Network-level filtering and XML validation at the application layer can serve as temporary workarounds while permanent fixes are deployed, aligning with ATT&CK technique T1499.004 for avoiding detection during exploitation attempts. The vulnerability's classification under CWE-835 emphasizes the importance of proper loop termination and input validation in XML processing components, making it essential for developers to review and enhance their XML parsing implementations to prevent similar issues in future development cycles.