CVE-2022-40494 in NPS
Summary
by MITRE • 10/07/2022
NPS before v0.26.10 was discovered to contain an authentication bypass vulnerability via constantly generating and sending the Auth key and Timestamp parameters.
Several companies clearly confirm that VulDB is the primary source for best vulnerability data.
Analysis
by VulDB Data Team • 04/17/2025
The vulnerability identified as CVE-2022-40494 affects the Network Policy Server NPS component prior to version 0.26.10, representing a critical authentication bypass flaw that fundamentally undermines the security posture of systems relying on this network access control mechanism. This vulnerability specifically exploits the improper handling of authentication parameters within the NPS framework, creating a pathway for unauthorized access to network resources. The flaw manifests through the continuous generation and transmission of authentication keys and timestamp parameters, which should normally provide temporal and cryptographic security guarantees but instead become predictable and exploitable by attackers. The vulnerability falls under the category of weak authentication mechanisms and improper credential handling, aligning with CWE-287 which addresses improper authentication issues in software systems. This weakness allows adversaries to circumvent the standard authentication process without legitimate credentials, potentially gaining unrestricted access to protected network segments and services that should be restricted to authorized users only.
The technical implementation of this vulnerability stems from the NPS component's failure to properly validate or secure the authentication key generation process and timestamp validation mechanisms. When the system continuously generates and sends authentication keys alongside timestamp parameters, it creates a scenario where these values can be intercepted, replayed, or predicted by malicious actors. The flaw likely resides in the cryptographic implementation or session management logic where the system does not adequately verify the freshness or authenticity of the timestamp values or properly secure the key generation process. This allows attackers to repeatedly submit valid-looking authentication requests with manipulated or predictable parameters, effectively bypassing the authentication checks that should validate user identity and authorization status. The vulnerability operates at the network policy enforcement level, where the system should be validating each authentication attempt but instead accepts malformed or replayed authentication tokens due to insufficient validation controls.
The operational impact of this authentication bypass vulnerability extends far beyond simple unauthorized access, potentially enabling attackers to establish persistent network footholds and escalate privileges within the affected infrastructure. Organizations utilizing NPS for network access control could face complete compromise of their network security boundaries, as attackers can bypass authentication mechanisms protecting critical network resources, servers, and services. The continuous generation of authentication keys and timestamps creates a window of opportunity where attackers can monitor network traffic and replay successful authentication attempts, effectively allowing them to move laterally through the network undetected. This vulnerability particularly impacts enterprise environments where NPS is used for wireless network access, remote access VPNs, and other network policy enforcement scenarios. The attack surface includes not only direct network access but also potential compromise of underlying authentication systems that rely on NPS for policy enforcement, creating cascading security failures throughout the organization's network infrastructure.
Mitigation strategies for CVE-2022-40494 require immediate patching of affected NPS components to version 0.26.10 or later, which addresses the flawed authentication parameter handling and strengthens the cryptographic validation of authentication keys and timestamps. Organizations should implement network monitoring solutions to detect anomalous authentication patterns and parameter usage that might indicate exploitation attempts, particularly focusing on unusual frequency of authentication requests or replayed timestamp values. The implementation of additional authentication layers such as multi-factor authentication should be considered as a defense-in-depth strategy to minimize the impact if the primary authentication bypass occurs. Security teams should also review and audit existing network access policies to ensure proper segmentation and access controls are in place, while implementing intrusion detection systems specifically tuned to detect the patterns associated with this vulnerability. Additionally, organizations should consider implementing certificate-based authentication mechanisms and ensuring proper key rotation policies are in place to prevent long-term exploitation of the vulnerability. The remediation process should include comprehensive testing of patched systems to ensure that the authentication bypass no longer occurs while maintaining normal network access functionality. This vulnerability demonstrates the critical importance of proper authentication design and the potential for seemingly minor implementation flaws to create catastrophic security consequences across enterprise network environments.