CVE-2021-22965 in Pulse Connect Secure
Summary
by MITRE • 11/19/2021
A vulnerability in Pulse Connect Secure before 9.1R12.1 could allow an unauthenticated administrator to causes a denial of service when a malformed request is sent to the device.
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Analysis
by VulDB Data Team • 10/17/2022
The vulnerability identified as CVE-2021-22965 represents a critical denial of service flaw affecting Pulse Connect Secure appliances running versions prior to 9.1R12.1. This vulnerability specifically targets the web administration interface of the Pulse Connect Secure platform, which serves as the primary management console for configuring and monitoring the secure access gateway. The affected system operates by processing incoming HTTP requests through its web server component, which handles both user authentication and administrative functions. When an attacker crafts a malformed request that exploits this vulnerability, the system fails to properly validate the incoming data, leading to a cascading failure that results in complete service disruption. The flaw exists within the request parsing logic where insufficient input validation allows specially crafted payloads to trigger unexpected behavior in the application's processing engine, ultimately causing the system to become unresponsive and unable to service legitimate requests.
This vulnerability falls under the category of CWE-129 Improper Validation of Input and can be mapped to ATT&CK technique T1499.004 Network Denial of Service within the context of network infrastructure attacks. The attack vector requires no authentication credentials, making it particularly dangerous as it can be exploited by anyone with network access to the vulnerable device. The malformed request payload typically consists of specially constructed HTTP headers or parameters that cause the web server to enter an infinite loop or consume excessive system resources during processing. The exploitation process involves sending a single malformed request that triggers a memory leak or resource exhaustion condition, causing the system to crash or become unresponsive. This vulnerability demonstrates a fundamental flaw in the application's defensive programming practices, where proper error handling and input sanitization mechanisms were either missing or insufficient to prevent malicious input from causing system instability.
The operational impact of CVE-2021-22965 extends beyond simple service disruption to potentially compromise the entire secure access infrastructure that organizations rely upon for remote network connectivity. When a Pulse Connect Secure appliance becomes unavailable due to this vulnerability, it affects all users who depend on the secure access gateway for remote work connectivity, VPN access, and secure network penetration. Organizations may experience significant downtime during business hours, leading to productivity losses and potential security gaps if alternative access methods are not immediately available. The vulnerability also creates a window of opportunity for more sophisticated attacks, as the compromised system may be temporarily unavailable for monitoring or logging activities, potentially masking other concurrent attacks. Additionally, the denial of service condition can affect the device's ability to maintain proper state information, which may result in configuration inconsistencies or data loss during recovery processes.
Mitigation strategies for CVE-2021-22965 should prioritize immediate patch deployment to version 9.1R12.1 or later, which includes proper input validation and request sanitization mechanisms. Organizations should implement network segmentation to limit access to administrative interfaces, restricting these endpoints to trusted management networks only. The implementation of web application firewalls and intrusion detection systems can provide additional layers of protection by monitoring for suspicious request patterns that match the vulnerability's exploitation signature. Regular security assessments and penetration testing should be conducted to identify similar input validation flaws in other network infrastructure components. System administrators should also configure proper monitoring and alerting mechanisms to detect unusual resource consumption patterns or service disruptions that may indicate exploitation attempts. The vulnerability serves as a reminder of the importance of maintaining current security patches and implementing defense-in-depth strategies that protect critical infrastructure components from both known and emerging threats. Organizations should also develop incident response procedures that specifically address denial of service vulnerabilities in network security appliances, ensuring rapid recovery and minimal business impact when such incidents occur.