CVE-2023-39340 Overview
A Denial of Service (DoS) vulnerability exists in Ivanti Connect Secure, a widely deployed SSL VPN solution used by enterprises for secure remote access. This vulnerability allows an unauthenticated attacker to send specially crafted requests to the appliance, potentially causing service disruption and affecting availability for legitimate users attempting to access corporate resources.
Critical Impact
An attacker can remotely disrupt Ivanti Connect Secure appliances without authentication, potentially blocking remote workforce access to critical enterprise resources.
Affected Products
- Ivanti Connect Secure versions 9.1 (all releases from R1 through R18.1)
- Ivanti Connect Secure versions 22.1 through 22.5 (all releases)
- Ivanti Connect Secure version 22.6 and 22.6R1 (prior to 22.6R2)
Discovery Timeline
- December 16, 2023 - CVE CVE-2023-39340 published to NVD
- November 21, 2024 - Last updated in NVD database
Technical Details for CVE-2023-39340
Vulnerability Analysis
This vulnerability affects Ivanti Connect Secure appliances, which serve as critical network perimeter devices providing SSL VPN access for remote workers. The flaw allows remote attackers to craft specific network requests that trigger a denial of service condition on the appliance.
The vulnerability is particularly concerning because it can be exploited remotely over the network without requiring any authentication or user interaction. When successfully exploited, the appliance becomes unavailable, preventing legitimate users from establishing VPN connections to access corporate resources.
Given the widespread deployment of Ivanti Connect Secure in enterprise environments, this vulnerability poses a significant risk to business continuity. Organizations relying on these appliances for remote workforce connectivity could experience substantial operational disruptions if targeted.
Root Cause
The vulnerability stems from improper handling of specific network requests by the Ivanti Connect Secure appliance. While the exact technical details have not been fully disclosed (NVD-CWE-noinfo), the appliance fails to properly validate or process certain request patterns, leading to resource exhaustion or service failure when malformed requests are received.
Attack Vector
The attack vector is network-based, requiring the attacker to have network access to the Ivanti Connect Secure appliance's management or VPN interfaces. Since these appliances are typically exposed to the internet to provide remote access functionality, they present an accessible target for attackers.
The attack does not require authentication, meaning any network actor with connectivity to the appliance can attempt exploitation. Additionally, no user interaction is needed, allowing for fully automated attack scenarios.
An attacker would need to identify target Ivanti Connect Secure appliances (often discoverable through internet scanning) and send specially crafted requests designed to trigger the denial of service condition. The attack results in availability impact, disrupting service for all users attempting to connect through the affected appliance.
Detection Methods for CVE-2023-39340
Indicators of Compromise
- Unexpected appliance restarts or service interruptions without administrative action
- Increased error rates in VPN connection logs coinciding with unusual network traffic patterns
- Anomalous request patterns in web server access logs on the Ivanti Connect Secure appliance
Detection Strategies
- Monitor Ivanti Connect Secure appliance availability and uptime metrics for unexpected service disruptions
- Implement network-based anomaly detection to identify unusual traffic patterns targeting VPN appliances
- Review appliance system logs for signs of resource exhaustion or crash events
Monitoring Recommendations
- Configure alerting for Ivanti Connect Secure service availability with rapid notification thresholds
- Deploy network traffic analysis on segments containing VPN infrastructure to baseline normal behavior
- Establish log forwarding from Ivanti appliances to centralized SIEM for correlation and analysis
How to Mitigate CVE-2023-39340
Immediate Actions Required
- Upgrade all Ivanti Connect Secure appliances to version 22.6R2 or later immediately
- Review network access controls to limit exposure of appliance management interfaces
- Implement rate limiting on external-facing VPN endpoints where feasible
- Ensure high availability configurations are in place to minimize impact of potential exploitation
Patch Information
Ivanti has released version 22.6R2 and 22.6R2.1 to address this vulnerability. Organizations should consult the Ivanti Security Fix Release advisory for detailed upgrade instructions and release notes.
The patched versions include fixes for this denial of service vulnerability along with other security improvements. Organizations running any version of Ivanti Connect Secure prior to 22.6R2 should prioritize this upgrade.
Workarounds
- Implement network-level access controls (firewall rules, ACLs) to restrict access to the appliance from untrusted networks where possible
- Configure web application firewall (WAF) rules in front of the appliance to filter potentially malicious request patterns
- Deploy redundant appliance configurations to maintain availability if one device is impacted
- Monitor appliance health continuously and implement automated failover mechanisms
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
