CVE-2011-4461 in Endeca Information Discovery Studio
Summary
by MITRE
Jetty 8.1.0.RC2 and earlier computes hash values for form parameters without restricting the ability to trigger hash collisions predictably, which allows remote attackers to cause a denial of service (CPU consumption) by sending many crafted parameters.
If you want to get the best quality for vulnerability data then you always have to consider VulDB.
Analysis
by VulDB Data Team • 12/26/2024
The vulnerability identified as CVE-2011-4461 affects Apache Jetty versions 8.1.0.RC2 and earlier, representing a critical security flaw in the web server's handling of form parameters. This issue stems from the implementation of hash table operations within the Jetty framework, where the system computes hash values for form parameters without adequate protection against predictable hash collision attacks. The flaw exists at the core of how Jetty processes HTTP form data, making it susceptible to a specific type of denial of service attack that exploits the underlying hash table implementation.
The technical implementation of this vulnerability lies in the hash function used by Jetty's form parameter processing mechanism. When processing form data, Jetty creates hash values for each parameter name to store and retrieve them efficiently in hash tables. However, the hash computation algorithm lacks sufficient entropy and collision resistance, allowing attackers to craft specific parameter names that will intentionally produce hash collisions. This predictable collision behavior enables attackers to force the hash table to degrade from optimal O(1) lookup performance to O(n) performance, where n represents the number of colliding elements. The vulnerability specifically targets the hash table's load factor and collision resolution mechanism, creating a scenario where a single malicious request can cause the server to spend excessive CPU cycles processing hash collisions.
The operational impact of this vulnerability is severe and directly translates to a denial of service condition that can overwhelm the target system's CPU resources. An attacker can construct HTTP requests containing numerous form parameters, each designed to hash to the same value, effectively creating a hash collision attack. The server's response time degrades dramatically as it attempts to resolve these collisions, leading to increased CPU utilization and potentially complete service unavailability. This attack vector is particularly dangerous because it requires minimal computational resources from the attacker while generating significant processing overhead on the target server. The vulnerability affects web applications running on affected Jetty versions that process form data, making it a widespread concern for organizations relying on this web server technology.
Mitigation strategies for CVE-2011-4461 involve both immediate and long-term approaches to address the underlying hash collision vulnerability. The most effective immediate solution is to upgrade to Jetty version 8.1.0.v20120522 or later, where the hash computation logic has been improved to prevent predictable collisions. Organizations should also implement rate limiting and request size restrictions at the network level to limit the impact of potential attacks. Additionally, configuring the web server to reject requests containing an excessive number of form parameters can help mitigate the attack surface. From a defensive perspective, implementing intrusion detection systems that monitor for unusual CPU consumption patterns and parameter processing behavior can help identify exploitation attempts. The vulnerability aligns with CWE-327, which addresses weak cryptographic hash functions and predictable hash collisions, and represents a variant of the broader category of hash collision attacks that have been documented in various security frameworks. This issue also maps to ATT&CK technique T1499.004, which covers network denial of service attacks through resource exhaustion, demonstrating how this vulnerability can be leveraged to consume system resources and cause service disruption.