CVE-2023-47106 in Traefik
Summary
by MITRE • 12/04/2023
Traefik is an open source HTTP reverse proxy and load balancer. When a request is sent to Traefik with a URL fragment, Traefik automatically URL encodes and forwards the fragment to the backend server. This violates RFC 7230 because in the origin-form the URL should only contain the absolute path and the query. When this is combined with another frontend proxy like Nginx, it can be used to bypass frontend proxy URI-based access control restrictions. This vulnerability has been addressed in versions 2.10.6 and 3.0.0-beta5. Users are advised to upgrade. There are no known workarounds for this vulnerability.
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Analysis
by VulDB Data Team • 12/23/2023
The vulnerability identified as CVE-2023-47106 affects Traefik, a widely deployed open source HTTP reverse proxy and load balancer that serves as a critical component in modern web infrastructure. This security flaw stems from Traefik's improper handling of URL fragments during request processing, creating a significant deviation from established web standards and potentially enabling unauthorized access to protected resources. The vulnerability represents a fundamental breakdown in Traefik's HTTP protocol compliance, specifically violating the requirements outlined in RFC 7230 which governs HTTP message syntax and routing.
The technical implementation of this vulnerability occurs when Traefik processes incoming requests containing URL fragments, which are typically used for client-side navigation within web pages and are intended to be processed by the user agent rather than forwarded to backend servers. Traefik's behavior of automatically URL encoding and forwarding these fragments to backend systems creates an unexpected communication channel that bypasses normal request processing. This flaw exists because Traefik incorrectly treats fragments as part of the origin-form of the HTTP request, which according to RFC 7230 should only contain the absolute path and query components. The improper handling of fragments creates a pathway where attackers can manipulate the request flow to access resources that should be restricted by URI-based access controls.
The operational impact of this vulnerability extends beyond simple protocol non-compliance to create real security risks in environments where Traefik operates as part of a larger proxy chain. When Traefik is deployed alongside other frontend proxies such as Nginx, the fragment forwarding behavior can be exploited to bypass access control mechanisms that rely on URI-based restrictions. This creates a scenario where an attacker could potentially access protected resources by manipulating the URL fragment to circumvent frontend proxy security policies. The vulnerability affects both Traefik version 2.10.5 and earlier versions, as well as the 3.0.0-beta4 release, indicating that this was a significant issue affecting multiple release streams and potentially exposing numerous production environments to unauthorized access.
Security researchers have classified this vulnerability in accordance with CWE-284, which addresses improper access control issues, and it aligns with ATT&CK technique T1071.004 for application layer protocol manipulation. The vulnerability demonstrates how seemingly minor protocol violations can create significant security implications when combined with other infrastructure components. Organizations using Traefik in production environments face potential exposure to data leakage, unauthorized access to protected resources, and bypass of security controls that depend on proper URI handling. The lack of known workarounds means that organizations must rely entirely on upgrading to patched versions, making this vulnerability particularly concerning for environments with strict deployment schedules or limited update capabilities.
The remediation for CVE-2023-47106 requires immediate action from affected organizations to upgrade to Traefik versions 2.10.6 or 3.0.0-beta5, which contain the necessary fixes to properly handle URL fragments according to RFC 7230 standards. Security teams should conduct comprehensive assessments of their Traefik deployments to identify any systems that may be vulnerable, particularly those operating in environments where fragment handling could impact access controls. Organizations should also review their overall proxy infrastructure to ensure that other components are not inadvertently relying on the flawed fragment handling behavior, as this vulnerability may have created unexpected communication pathways that could impact other security controls. The vulnerability highlights the importance of maintaining strict adherence to HTTP standards in security-critical infrastructure components and demonstrates how protocol compliance issues can create unexpected security implications.