CVE-2012-2739 in JDK
Summary
by MITRE
Oracle Java SE before 7 Update 6, and OpenJDK 7 before 7u6 build 12 and 8 before build 39, computes hash values without restricting the ability to trigger hash collisions predictably, which allows context-dependent attackers to cause a denial of service (CPU consumption) via crafted input to an application that maintains a hash table.
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Analysis
by VulDB Data Team • 03/04/2025
The vulnerability identified as CVE-2012-2739 represents a critical weakness in the Java runtime environment that affects both Oracle Java SE and OpenJDK implementations. This flaw resides in the hash table implementation mechanism where the system fails to properly limit the conditions under which hash collisions can be deliberately triggered. The vulnerability impacts Java versions prior to 7 Update 6 for Oracle Java SE and specific OpenJDK versions before their respective security patches. The technical root cause stems from the hash computation algorithm's inability to prevent predictable collision scenarios, creating an avenue for malicious actors to exploit the underlying hash table data structure.
The operational impact of this vulnerability manifests as a severe denial of service condition where an attacker can consume excessive CPU resources by providing specifically crafted input data to applications that utilize hash tables. When the hash table encounters these crafted inputs, it becomes vulnerable to a hash collision attack that causes the hash table to degrade from optimal O(1) lookup performance to O(n) performance, where n represents the number of elements in the hash table. This degradation results in exponential CPU consumption as the application attempts to resolve collisions within the hash structure. The vulnerability is particularly dangerous because it requires minimal input to trigger significant performance degradation, making it an attractive vector for attackers seeking to disrupt service availability.
The security implications extend beyond simple resource exhaustion, as this vulnerability directly relates to CWE-400, which addresses the weakness of uncontrolled resource consumption. Attackers can leverage this flaw to perform denial of service attacks against Java applications without requiring elevated privileges or complex exploitation techniques. The attack vector is context-dependent, meaning that the vulnerability only affects applications that maintain hash table structures and process user-supplied input through these data structures. This characteristic makes the vulnerability particularly insidious as it can be exploited against a wide range of Java applications including web applications, enterprise systems, and server-side applications that rely on hash-based data structures for efficient data management. The vulnerability aligns with ATT&CK technique T1499.004, which covers network denial of service attacks through resource exhaustion, making it a significant concern for organizations relying on Java-based systems.
Organizations should prioritize immediate patching of affected systems to address this vulnerability, particularly focusing on upgrading to Oracle Java SE 7 Update 6 or later versions, and OpenJDK versions that include the relevant security fixes. System administrators should also implement monitoring solutions to detect unusual CPU consumption patterns that may indicate exploitation attempts. The mitigation strategy should include regular security assessments of Java applications to identify hash table usage patterns and ensure that input validation mechanisms are properly implemented to prevent malicious input from reaching hash table processing components. Additionally, application-level protections such as hash table size limits and input sanitization routines should be considered as defensive measures to reduce the impact of potential exploitation attempts.