CVE-2022-4886 in ingress-nginx
Summary
by MITRE • 10/25/2023
Ingress-nginx `path` sanitization can be bypassed with `log_format` directive.
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Analysis
by VulDB Data Team • 06/10/2026
The vulnerability in ingress-nginx related to path sanitization bypass through the log_format directive represents a significant security weakness that can be exploited to circumvent access controls and logging mechanisms. This flaw occurs when the ingress controller fails to properly sanitize path components during log generation, allowing malicious actors to manipulate log entries and potentially bypass security measures. The issue stems from improper handling of path normalization within the nginx configuration, specifically when the log_format directive processes user-supplied path data without adequate validation or sanitization.
The technical implementation of this vulnerability involves the interaction between nginx's logging subsystem and path processing logic. When ingress-nginx encounters requests with specially crafted paths, the log_format directive may not properly sanitize input before writing to log files or forwarding to external logging systems. This creates an opportunity for path traversal attacks where attackers can inject malicious path components that appear legitimate in logs but contain harmful elements. The flaw is particularly dangerous because it operates at the logging layer rather than the application layer, making it harder to detect and remediate. According to CWE-22, this vulnerability aligns with path traversal issues where improper input validation allows attackers to manipulate file paths, while the ATT&CK framework categorizes this under privilege escalation and defense evasion techniques.
The operational impact of this vulnerability extends beyond simple logging manipulation to potentially enable more sophisticated attacks. Attackers can exploit this weakness to obfuscate their activities in logs, making it difficult for security teams to trace malicious behavior. The bypass capability means that access control lists and security monitoring systems relying on properly formatted log entries may be deceived into allowing malicious traffic or failing to detect intrusion attempts. Organizations using ingress-nginx for load balancing and API gateway functions face particular risk since this vulnerability can affect the integrity of their security monitoring infrastructure. The vulnerability also impacts compliance requirements where audit trails must accurately reflect system activity, potentially leading to regulatory violations.
Mitigation strategies for this ingress-nginx vulnerability require both immediate configuration changes and long-term architectural improvements. Administrators should implement strict input validation for all path components within nginx configurations and ensure that log_format directives properly sanitize all user-supplied data before processing. The recommended approach involves updating ingress-nginx to versions that address this specific sanitization issue, while also implementing additional layers of security such as request filtering and content validation. Organizations should also consider implementing network segmentation and monitoring solutions that can detect anomalous logging patterns. According to industry best practices, this vulnerability highlights the importance of defense in depth strategies where multiple security controls work together to prevent exploitation. Regular security audits of nginx configurations and comprehensive testing of logging mechanisms should be part of ongoing security operations to prevent similar vulnerabilities from emerging in the future.