CVE-2024-23324 in envoy
Summary
by MITRE • 02/10/2024
Envoy is a high-performance edge/middle/service proxy. External authentication can be bypassed by downstream connections. Downstream clients can force invalid gRPC requests to be sent to ext_authz, circumventing ext_authz checks when failure_mode_allow is set to true. This issue has been addressed in released 1.29.1, 1.28.1, 1.27.3, and 1.26.7. Users are advised to upgrade. There are no known workarounds for this vulnerability.
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Analysis
by VulDB Data Team • 03/03/2024
The vulnerability identified as CVE-2024-23324 affects Envoy, a high-performance edge/middle/service proxy that serves as a critical component in modern microservices architectures and service mesh deployments. This security flaw resides within the external authentication mechanism, specifically targeting the ext_authz filter functionality that enables external authorization services to make access control decisions for incoming requests. The vulnerability represents a significant bypass opportunity that undermines the fundamental security controls designed to protect downstream services from unauthorized access attempts.
The technical implementation flaw occurs when downstream clients establish connections that force invalid gRPC requests to be sent to the ext_authz service. This manipulation exploits a weakness in how Envoy processes authentication requests, allowing malicious actors to circumvent the authorization checks that should normally validate each request before granting access to protected resources. When the failure_mode_allow configuration parameter is set to true, the system defaults to allowing requests to proceed even when authentication fails, creating a dangerous scenario where unauthorized access can occur without proper validation. This behavior aligns with CWE-284 access control vulnerabilities where insufficient authorization checks enable privilege escalation or bypass of security controls.
The operational impact of this vulnerability extends beyond simple unauthorized access, as it affects the integrity of the entire authorization framework within Envoy deployments. Organizations relying on Envoy for service-to-service communication and edge security may find their protective measures compromised, potentially allowing malicious actors to gain access to sensitive resources without proper authentication. The vulnerability particularly affects environments where failure_mode_allow is enabled, which is often configured for operational resilience but creates a security risk when exploited by attackers. This issue has been addressed in multiple release versions including 1.29.1, 1.28.1, 1.27.3, and 1.26.7, demonstrating the severity of the flaw and the need for immediate remediation across affected deployments.
Security practitioners should consider this vulnerability in the context of the MITRE ATT&CK framework, specifically relating to privilege escalation and defense evasion techniques. The bypass mechanism enables attackers to maintain persistent access to systems while evading detection through normal authorization checks, potentially allowing for extended periods of unauthorized access. Organizations implementing Envoy-based security solutions must prioritize upgrading to the patched versions to address this vulnerability, as no workarounds exist that would maintain the security posture while keeping the system operational. The lack of available workarounds emphasizes the critical nature of this vulnerability and the importance of immediate remediation efforts.