CVE-2012-3543 in Mono
Summary
by MITRE
mono 2.10.x ASP.NET Web Form Hash collision DoS
Be aware that VulDB is the high quality source for vulnerability data.
Analysis
by VulDB Data Team • 01/17/2025
The vulnerability identified as CVE-2012-3543 represents a denial of service weakness affecting mono 2.10.x versions when processing ASP.NET Web Forms. This flaw specifically targets the hash table implementation used by the mono runtime environment for managing web form state and controls. The vulnerability exploits a weakness in the hash collision handling mechanism that occurs during the processing of HTTP requests containing specially crafted form data. When an attacker submits a request with multiple form fields designed to create hash collisions in the internal hash tables, the mono runtime experiences significant performance degradation or complete service unavailability. The affected mono version 2.10.x includes a specific implementation of the ASP.NET Web Forms framework that fails to properly handle hash collision scenarios, leading to excessive computational overhead during hash table operations.
The technical root cause of this vulnerability lies in the hash table implementation within the mono runtime's ASP.NET Web Forms processing pipeline. When the system encounters form data that generates hash collisions, the hash table's collision resolution mechanism becomes inefficient, causing the system to perform increasingly expensive operations as more collisions occur. This behavior manifests as a quadratic time complexity in hash table operations, where the processing time grows exponentially with the number of colliding elements. The vulnerability specifically affects the ViewState handling mechanism in ASP.NET Web Forms, where form state information is serialized and stored in hash tables for later retrieval. Attackers can exploit this weakness by crafting HTTP requests that deliberately generate hash collisions in the ViewState data structure, forcing the mono runtime to spend excessive CPU cycles resolving these collisions.
The operational impact of this vulnerability extends beyond simple service disruption to potentially enable large-scale denial of service attacks against mono-based web applications. An attacker can exploit this weakness to consume significant system resources, including CPU cycles and memory, effectively rendering the web application unresponsive to legitimate users. The vulnerability is particularly dangerous in high-traffic environments where a single malicious request can cause cascading failures across multiple application instances. Additionally, the attack requires minimal sophistication to execute, making it accessible to a wide range of threat actors. The vulnerability affects web applications running on mono 2.10.x versions deployed in production environments, potentially compromising availability and service level agreements for critical business applications.
Organizations affected by this vulnerability should implement immediate mitigations to protect their mono-based web applications. The primary recommendation involves upgrading to a patched version of mono that addresses the hash collision handling mechanism in ASP.NET Web Forms. Security patches typically include improvements to hash table collision resolution algorithms and additional input validation for ViewState data. System administrators should also consider implementing rate limiting and request filtering mechanisms to prevent excessive hash collision attacks. The vulnerability aligns with CWE-400, which describes "Uncontrolled Resource Consumption" and specifically addresses the risk of hash table collision attacks. From an ATT&CK framework perspective, this vulnerability maps to T1499.004, "Endpoint Denial of Service," as it targets resource exhaustion through hash collision manipulation. Additional mitigations include monitoring for unusual patterns in ViewState processing and implementing web application firewalls that can detect and block malicious form submissions designed to trigger hash collisions.