CVE-2012-3514 in OCaml Xml-Light Library
Summary
by MITRE
OCaml Xml-Light Library before r234 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 unspecified vectors.
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Analysis
by VulDB Data Team • 12/12/2021
The vulnerability identified as CVE-2012-3514 affects the OCaml Xml-Light Library version r234 and earlier, presenting a significant security risk through predictable hash collision exploitation. This flaw resides in the library's hash table implementation where hash values are computed without adequate measures to prevent attackers from deliberately triggering collision conditions. The vulnerability operates under the principle that when an attacker can predictably cause hash collisions, they can manipulate the hash table structure to degrade performance significantly.
The technical implementation flaw stems from insufficient hash function design within the Xml-Light library, allowing malicious inputs to consistently map to the same hash bucket. This creates a scenario where hash table operations that should typically execute in constant time O(1) instead degrade to linear time O(n) performance, where n represents the number of colliding elements. The vulnerability is classified under CWE-254 as a weakness related to inadequate input validation and improper handling of hash functions. Attackers can exploit this by crafting specific inputs that will consistently hash to the same value, forcing the system to traverse collision chains repeatedly.
The operational impact of this vulnerability manifests as a denial of service condition where computational resources become consumed excessively. When an attacker successfully triggers predictable hash collisions, the system experiences dramatic performance degradation as CPU cycles are consumed processing the increasingly long collision chains. This vulnerability is context-dependent, meaning that the attack requires specific conditions to be effective, such as the ability to influence input data that gets processed through the vulnerable hash table. The attack vector typically involves sending specially crafted XML data that will be parsed by the Xml-Light library, causing the hash table to become increasingly inefficient.
From an adversarial perspective, this vulnerability aligns with ATT&CK technique T1499.004 which covers network denial of service attacks, and specifically targets the resource exhaustion aspect of system compromise. The attack can be executed with relatively simple input manipulation techniques, making it accessible to attackers with basic knowledge of hash collision principles. Organizations using the affected library in web applications, XML processing services, or any system that relies on hash table lookups for performance-critical operations are at risk of experiencing service disruption. The vulnerability's impact extends beyond immediate denial of service to potentially affecting system availability and responsiveness, particularly in environments where the Xml-Light library is heavily utilized for processing XML data.
The recommended mitigations include upgrading to version r234 or later of the OCaml Xml-Light Library where the hash collision vulnerability has been addressed through improved hash function implementation. Additionally, organizations should implement input validation and sanitization measures to reduce the likelihood of malicious inputs reaching the vulnerable hash table operations. System administrators should monitor for unusual CPU consumption patterns that might indicate hash collision attacks, and consider implementing rate limiting or input size restrictions for XML processing components. The fix typically involves using a more robust hash function or implementing randomized hash functions that make predictable collisions significantly more difficult to achieve.