CVE-2023-5044 in ingress-nginx
Summary
by MITRE • 10/25/2023
Code injection via nginx.ingress.kubernetes.io/permanent-redirect annotation.
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Analysis
by VulDB Data Team • 02/14/2025
The vulnerability identified as CVE-2023-5044 represents a critical code injection flaw within the nginx ingress controller for kubernetes environments. This security weakness specifically manifests through the nginx.ingress.kubernetes.io/permanent-redirect annotation which allows attackers to inject arbitrary code into the nginx configuration. The vulnerability stems from insufficient input validation and sanitization of user-supplied data within the ingress controller's annotation processing logic. When administrators or attackers define permanent redirect configurations using this annotation, the system fails to properly escape or validate the input parameters before incorporating them into the nginx configuration files. This oversight creates a pathway for malicious actors to execute arbitrary code within the context of the nginx process, potentially leading to complete system compromise.
The technical exploitation of this vulnerability occurs when an attacker crafts malicious input within the permanent-redirect annotation value. The nginx ingress controller processes this annotation without adequate sanitization, allowing special characters and code sequences to be interpreted by the nginx configuration parser. This behavior aligns with CWE-94, which describes improper control of generation of code, and specifically relates to CWE-74, which covers injection flaws. The attack vector leverages the ingress controller's configuration management system, where user-defined annotations are translated into nginx directives. When the nginx process reloads its configuration, the injected code executes with the privileges of the nginx process, potentially enabling attackers to access sensitive system resources, escalate privileges, or perform unauthorized operations.
The operational impact of CVE-2023-5044 extends beyond immediate code execution capabilities to encompass broader system compromise and data exposure risks. Organizations utilizing nginx ingress controllers with vulnerable versions face potential unauthorized access to their kubernetes clusters, as the injected code can manipulate network traffic routing, access application data, or establish persistence mechanisms. The vulnerability affects the entire ingress controller configuration pipeline, making it particularly dangerous in multi-tenant environments where multiple applications share the same ingress controller instance. Attackers can leverage this flaw to redirect traffic to malicious endpoints, intercept sensitive communications, or gain access to backend services. The impact is amplified when considering that ingress controllers often serve as the primary entry point for external traffic into kubernetes clusters, making them attractive targets for attackers seeking to establish persistent access or conduct reconnaissance activities.
Mitigation strategies for CVE-2023-5044 focus on both immediate remediation and long-term security hardening measures. Organizations should prioritize updating their nginx ingress controller deployments to versions that address this vulnerability, typically those released after the initial disclosure. The immediate fix involves implementing strict input validation and sanitization for all annotation values, particularly those related to redirect configurations. Security teams should also consider implementing network segmentation and access controls to limit who can modify ingress controller configurations. Additional protective measures include enabling pod security policies that restrict the capabilities of ingress controller pods, implementing runtime application protection mechanisms, and conducting regular security audits of ingress controller configurations. From an ATT&CK framework perspective, this vulnerability maps to techniques involving command and control communications and privilege escalation, making it essential for organizations to monitor for suspicious network traffic patterns and unauthorized configuration changes. Regular vulnerability assessments and penetration testing should be conducted to identify similar injection flaws in other components of the kubernetes infrastructure stack.