CVE-2024-37082: Cloud Foundry mTLS Auth Bypass Flaw

CVE-2024-37082 Overview

CVE-2024-37082 is a critical authentication bypass vulnerability affecting Cloud Foundry deployments that use the haproxy-boshrelease with a non-default configuration. When route-services are enabled in routing-release and the HAProxy property ha_proxy.forwarded_client_cert is configured to forward_only_if_route_service, attackers can craft malicious HTTP requests that bypass mutual TLS (mTLS) authentication to Cloud Foundry applications.

This vulnerability falls under the CWE-290 (Authentication Bypass by Spoofing) classification, allowing unauthorized access to applications that rely on mTLS for client authentication.

Critical Impact

Attackers can bypass mTLS authentication controls to gain unauthorized access to protected Cloud Foundry applications, potentially compromising confidential data and application integrity.

Affected Products

• Cloud Foundry deployments using haproxy-boshrelease
• Configurations with route-services enabled in routing-release
• Systems with ha_proxy.forwarded_client_cert set to forward_only_if_route_service

Discovery Timeline

• 2024-07-03 - CVE-2024-37082 published to NVD
• 2024-11-21 - Last updated in NVD database

Technical Details for CVE-2024-37082

Vulnerability Analysis

This authentication bypass vulnerability occurs in the interaction between Cloud Foundry's routing layer and HAProxy when handling client certificate forwarding. The vulnerability specifically affects deployments where route-services are enabled and a particular HAProxy configuration is in use.

The flaw allows attackers to craft HTTP requests that manipulate the certificate forwarding mechanism, effectively bypassing mTLS authentication requirements. Since mTLS is commonly used to ensure only authorized clients can communicate with specific applications, this bypass undermines a critical security control.

The vulnerability enables network-based attacks without requiring prior authentication or user interaction. Successful exploitation could lead to unauthorized access to sensitive application data and the ability to modify application state without proper authentication.

Root Cause

The root cause lies in improper authentication handling (CWE-290) within the certificate forwarding logic of haproxy-boshrelease. When the ha_proxy.forwarded_client_cert property is configured to forward_only_if_route_service, the system fails to properly validate and enforce mTLS authentication requirements under certain conditions.

The configuration creates a trust relationship that can be exploited through carefully crafted HTTP requests, allowing attackers to spoof or bypass the expected client certificate validation process.

Attack Vector

The attack is network-based, requiring no privileges or user interaction. An attacker with network access to the Cloud Foundry deployment can craft malicious HTTP requests that exploit the certificate forwarding configuration to bypass mTLS authentication.

The attack involves manipulating HTTP headers or request properties in a way that causes HAProxy to forward requests as if they came from authenticated route-services, when in fact no valid client certificate authentication occurred.

For detailed technical information about the exploitation mechanism, refer to the Cloud Foundry security advisory.

Detection Methods for CVE-2024-37082

Indicators of Compromise

• Unusual access patterns to mTLS-protected applications from unexpected sources
• HTTP requests with manipulated or suspicious certificate-related headers
• Authentication logs showing access to protected resources without corresponding mTLS handshakes
• Increased traffic patterns to applications that should only be accessible via route-services

Detection Strategies

• Monitor HAProxy access logs for requests to protected endpoints that lack proper mTLS authentication
• Implement anomaly detection for traffic patterns to applications protected by mTLS
• Review authentication logs for discrepancies between expected and actual mTLS sessions
• Configure alerts for access to sensitive applications from unexpected network segments

Monitoring Recommendations

• Enable verbose logging on HAProxy to capture certificate forwarding decisions
• Implement log correlation between HAProxy and Cloud Foundry router logs
• Deploy network monitoring to detect unauthorized access attempts to protected applications
• Establish baseline traffic patterns for mTLS-protected applications to identify anomalies

How to Mitigate CVE-2024-37082

Immediate Actions Required

• Review your Cloud Foundry deployment configuration to determine if you are affected
• Check if route-services are enabled in routing-release
• Verify the ha_proxy.forwarded_client_cert property setting in your haproxy-boshrelease configuration
• Consider temporarily disabling route-services or changing the forwarded_client_cert configuration if immediate patching is not possible

Patch Information

Organizations running affected Cloud Foundry deployments should consult the official Cloud Foundry security advisory for specific patch information and updated versions of haproxy-boshrelease that address this vulnerability.

Apply patches to haproxy-boshrelease and routing-release components as soon as updated versions become available from Cloud Foundry.

Workarounds

• Change the ha_proxy.forwarded_client_cert configuration to a more secure setting if route-service functionality is not required
• Implement additional network-level access controls to restrict which sources can reach mTLS-protected applications
• Deploy Web Application Firewall (WAF) rules to detect and block suspicious certificate-related header manipulation
• Consider implementing defense-in-depth by adding application-level authentication in addition to mTLS

# Review current HAProxy configuration
# Check the forwarded_client_cert property in your BOSH manifest
bosh -d cf manifest | grep -A5 "ha_proxy:"

# Verify route-services configuration
bosh -d cf manifest | grep -i "route_services"

# If affected, consider updating the configuration
# Change from:
#   ha_proxy.forwarded_client_cert: forward_only_if_route_service
# To a more secure option per Cloud Foundry guidance