CVE-2009-1096 in JRE
Summary
by MITRE
Buffer overflow in unpack200 in Java SE Development Kit (JDK) and Java Runtime Environment (JRE) 5.0 Update 17 and earlier, and 6 Update 12 and earlier, allows remote attackers to access files or execute arbitrary code via a JAR file with crafted Pack200 headers.
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Analysis
by VulDB Data Team • 08/09/2021
The vulnerability identified as CVE-2009-1096 represents a critical buffer overflow flaw within the unpack200 utility of Oracle's Java SE Development Kit and Runtime Environment. This vulnerability specifically affects Java versions 5.0 Update 17 and earlier, as well as Java 6 Update 12 and earlier releases, making it a long-standing security issue that has impacted numerous enterprise environments. The flaw exists in the Pack200 unpacking functionality which is responsible for decompressing and processing JAR files that have been compressed using the Pack200 format. The buffer overflow occurs when the system processes malformed Pack200 headers within JAR files, creating an exploitable condition that can be leveraged by remote attackers to gain unauthorized access to system resources.
The technical implementation of this vulnerability stems from inadequate input validation within the unpack200 utility's parsing routine for Pack200 file headers. When a malicious JAR file containing crafted Pack200 headers is processed, the utility fails to properly bounds-check the data structures used to store header information, leading to memory corruption that can be exploited to overwrite adjacent memory locations. This type of vulnerability maps directly to CWE-121, which categorizes buffer overflow conditions where insufficient bounds checking allows attackers to write beyond allocated memory boundaries. The flaw operates at the binary parsing level, making it particularly dangerous as it can be triggered simply by opening or processing a malicious JAR file, regardless of the user's privileges or the specific system configuration.
The operational impact of CVE-2009-1096 extends beyond simple code execution to encompass potential unauthorized file access and system compromise across enterprise environments. Attackers can leverage this vulnerability to execute arbitrary code on systems running affected Java versions, potentially leading to complete system compromise, data exfiltration, or persistent backdoor installation. The vulnerability is particularly concerning in web application environments where JAR files might be processed automatically, as it can be exploited through web browsers or application servers that handle Java applets or web applications. Organizations using legacy Java installations are especially at risk, as the vulnerability exists in versions that may still be in production use despite being years old. This represents a significant attack surface that aligns with ATT&CK technique T1059.007 for command and scripting interpreter, as successful exploitation can lead to arbitrary code execution that can be used to establish further footholds within networks.
Mitigation strategies for CVE-2009-1096 require immediate patching of affected Java installations to the latest available versions that contain fixes for the buffer overflow condition. Organizations should implement comprehensive patch management procedures to ensure all Java installations are updated to versions that have resolved this vulnerability. Additionally, network segmentation and application whitelisting can help reduce the attack surface by limiting which systems can process JAR files or access Java-based applications. Security monitoring should be enhanced to detect unusual file processing activities that might indicate exploitation attempts, particularly around Pack200 file handling. System administrators should also consider disabling the unpack200 utility when it is not required for business operations, as this can eliminate the attack vector entirely. Regular vulnerability assessments and security audits should be conducted to identify any remaining systems running vulnerable Java versions, as this vulnerability has been classified as high-risk by multiple security organizations and continues to be exploited in targeted attacks against legacy systems.