CVE-2012-5373 in Java JDK
Summary
by MITRE
Oracle Java SE 7 and earlier, and OpenJDK 7 and earlier, computes hash values without properly 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, as demonstrated by a universal multicollision attack against the MurmurHash3 algorithm, a different vulnerability than CVE-2012-2739.
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Analysis
by VulDB Data Team • 04/22/2017
The vulnerability described in CVE-2012-5373 represents a critical weakness in the implementation of hash table algorithms within Java SE and OpenJDK versions 7 and earlier. This flaw specifically targets the hash computation mechanism that underlies hash table operations, creating a predictable collision scenario that can be exploited by malicious actors. The vulnerability affects the fundamental data structures used in Java applications, particularly those that rely heavily on hash-based collections such as HashMap, HashSet, and Hashtable. When applications process user input through these hash-based data structures, attackers can craft specific inputs designed to trigger hash collisions, leading to performance degradation and potential system instability.
The technical implementation of this vulnerability stems from the inadequate handling of hash value computation in the MurmurHash3 algorithm, which was used by Java's internal hash table implementations. This weakness allows attackers to construct input data that will consistently map to the same hash bucket, effectively transforming the expected O(1) hash table operations into O(n) linear searches. The vulnerability is particularly concerning because it operates at the algorithmic level rather than the application level, meaning that any Java application using hash tables is potentially vulnerable regardless of its specific implementation. The universal multicollision attack demonstrated against MurmurHash3 exploits the mathematical properties of the hash function to generate multiple inputs that produce identical hash values, creating a cascade of collisions that can overwhelm the system's processing capabilities.
From an operational impact perspective, this vulnerability creates a significant denial of service condition that can severely impact system performance and availability. When exploited, the vulnerability causes CPU consumption to spike dramatically as the hash table operations degenerate into inefficient linear searches, potentially consuming 100% of available CPU resources. The attack is context-dependent, meaning that it requires the target application to be processing specific types of input through hash-based data structures, but the impact can be devastating to system availability. This vulnerability affects not only individual applications but can potentially impact entire systems when multiple applications are running simultaneously and all utilize hash-based collections. The attack vector is particularly dangerous because it can be executed remotely without requiring authentication, making it a preferred method for attackers seeking to disrupt services.
The mitigation strategies for this vulnerability involve both immediate patching and architectural considerations for affected systems. Oracle and OpenJDK maintainers released updates that addressed the hash collision vulnerability by implementing stronger hash computation algorithms and introducing additional protections against predictable collision attacks. Organizations should prioritize updating their Java installations to versions that contain the patched hash implementations, typically Java 8 or later, which contain improved hash functions that are resistant to these types of attacks. Additionally, developers should consider implementing defensive programming practices such as using alternative data structures, implementing input validation and sanitization, and monitoring hash table performance metrics to detect potential attacks. This vulnerability aligns with CWE-327, which addresses weak cryptographic algorithms, and relates to ATT&CK technique T1499.004, which covers network denial of service attacks. Organizations should also implement network monitoring and intrusion detection systems to identify potential exploitation attempts and establish incident response procedures to address hash collision attacks that may occur in production environments.