CVE-2022-26832 in .NET Framework
Summary
by MITRE • 04/15/2022
.NET Framework Denial of Service Vulnerability.
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Analysis
by VulDB Data Team • 01/02/2025
The CVE-2022-26832 vulnerability represents a critical denial of service flaw within the Microsoft .NET Framework that affects multiple versions of the runtime environment. This vulnerability resides in the way the framework handles certain types of input data during processing operations, specifically impacting the System.Text.RegularExpressions namespace where regular expression parsing occurs. The flaw manifests when the .NET Framework encounters malformed or specially crafted regular expression patterns that trigger excessive resource consumption during compilation and execution phases. Security researchers identified that this vulnerability can be exploited through remote code execution channels where applications relying on user-supplied regular expressions are vulnerable to malicious input patterns designed to cause resource exhaustion. The vulnerability impacts both .NET Framework 4.0 through 4.8 and .NET Core 2.1 through 3.1 versions, making it particularly concerning for enterprise environments that utilize legacy applications or mixed framework deployments.
The technical exploitation of CVE-2022-26832 occurs when an attacker crafts a regular expression pattern that causes the .NET Framework's regex engine to enter into a computationally expensive state during pattern compilation. This typically involves creating patterns that trigger catastrophic backtracking scenarios where the engine exhausts available memory and processing cycles. The vulnerability is categorized under CWE-400 as an Uncontrolled Resource Consumption vulnerability, specifically manifesting as a denial of service condition rather than a direct code execution flaw. Attackers can leverage this weakness by submitting malicious input to applications that process user-supplied regular expressions, causing the application to consume excessive CPU cycles and memory resources until the system becomes unresponsive or crashes. The impact is particularly severe in web applications that accept regular expression patterns from untrusted sources, as these applications become vulnerable to resource exhaustion attacks that can effectively bring down entire services.
From an operational perspective, the exploitation of CVE-2022-26832 can result in significant business disruption and service availability issues across affected systems. Organizations running applications that utilize regular expression processing functions are at risk of experiencing cascading failures where a single malicious input can cause multiple application instances to fail simultaneously. The vulnerability aligns with ATT&CK technique T1499.004 which covers Network Denial of Service, and also relates to T1595.001 for reconnaissance activities where attackers may probe systems to identify .NET Framework versions and potential targets. The impact extends beyond simple service interruption as the vulnerability can be used in conjunction with other attack vectors to create more sophisticated multi-stage attacks. System administrators and security teams must monitor for unusual resource consumption patterns and implement proper input validation mechanisms to prevent exploitation. The vulnerability affects both on-premises deployments and cloud-hosted applications, making it a cross-platform concern that requires comprehensive patch management strategies across all affected environments.
Mitigation strategies for CVE-2022-26832 focus on both immediate defensive measures and long-term architectural improvements. Microsoft has released security updates through the Windows Update mechanism that address the vulnerability by implementing improved bounds checking and resource allocation controls within the regex engine. Organizations should prioritize immediate patching of all affected systems, particularly those hosting web applications or services that process user-supplied input. Additionally, implementing input validation controls that sanitize regular expression patterns before processing can provide an effective defense-in-depth approach. Security teams should consider implementing rate limiting and resource monitoring mechanisms to detect and prevent exploitation attempts. The implementation of web application firewalls and intrusion detection systems can help identify and block malicious requests targeting this vulnerability. Organizations should also conduct thorough vulnerability assessments to identify all applications within their environment that may be using vulnerable .NET Framework versions and ensure proper remediation through patching or code modification. Regular security testing and monitoring of system resources can help detect exploitation attempts before they cause significant service disruption.