CVE-2023-41327 in WireMock
Summary
by MITRE • 09/07/2023
WireMock is a tool for mocking HTTP services. WireMock can be configured to only permit proxying (and therefore recording) to certain addresses. This is achieved via a list of allowed address rules and a list of denied address rules, where the allowed list is evaluated first.
Until WireMock Webhooks Extension 3.0.0-beta-15, the filtering of target addresses from the proxy mode DID NOT work for Webhooks, so the users were potentially vulnerable regardless of the `limitProxyTargets` settings. Via the WireMock webhooks configuration, POST requests from a webhook might be forwarded to an arbitrary service reachable from WireMock’s instance. For example, If someone is running the WireMock docker Container inside a private cluster, they can trigger internal POST requests against unsecured APIs or even against secure ones by passing a token, discovered using another exploit, via authentication headers. This issue has been addressed in versions 2.35.1 and 3.0.3 of wiremock. Wiremock studio has been discontinued and will not see a fix. Users unable to upgrade should use external firewall rules to define the list of permitted destinations.
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Analysis
by VulDB Data Team • 10/02/2023
WireMock serves as a critical tool for HTTP service mocking and testing within development environments, providing developers with the ability to simulate various service behaviors and responses. The platform includes sophisticated proxy capabilities that allow it to forward requests to external services while maintaining control over which destinations are accessible through its proxy mode. This functionality relies on a security model that employs allowed address rules followed by denied address rules, creating a filtering mechanism designed to prevent unauthorized access to internal systems during proxy operations. The implementation of these rules is fundamental to maintaining network security boundaries, particularly in containerized environments where WireMock instances may be deployed within private clusters or restricted network zones.
The vulnerability identified as CVE-2023-41327 represents a critical flaw in the WireMock Webhooks Extension where the proxy address filtering mechanism fails to properly enforce security restrictions for webhook operations. This issue specifically affects versions prior to 3.0.0-beta-15 of the Webhooks Extension, creating a scenario where webhook configurations can bypass the intended `limitProxyTargets` security settings. The technical flaw stems from the fact that while WireMock correctly implements address filtering for standard proxy operations, the webhook component operates outside of this security boundary, allowing POST requests from webhooks to be forwarded to any arbitrary destination reachable from the WireMock instance. This represents a direct violation of the principle of least privilege and creates a potential attack vector that could be exploited by malicious actors.
The operational impact of this vulnerability extends beyond simple configuration oversight, creating serious security implications for organizations that rely on WireMock within private network environments. When running within a private cluster, WireMock instances may have access to internal services that are not intended to be exposed through the mocking framework. Attackers could potentially leverage this vulnerability to trigger internal POST requests against unsecured APIs or even against protected services by passing authentication tokens discovered through other exploits. This threat model aligns with ATT&CK technique T1190 for Proxying and T1071.004 for Application Layer Protocol: DNS, as the vulnerability enables unauthorized data exfiltration and lateral movement within network boundaries. The vulnerability particularly affects environments where WireMock is used for integration testing, API mocking, or load testing scenarios where the tool may be exposed to untrusted input or where internal network access is not properly segmented.
The security implications of this vulnerability are significant enough to warrant immediate attention from security teams and system administrators. Organizations using WireMock in production or staging environments may be unknowingly exposing their internal services to potential exploitation, especially when running within containerized environments where network segmentation is not properly enforced. The vulnerability creates a persistent risk where legitimate webhook configurations can be abused to access internal systems, potentially leading to data breaches, service disruption, or further compromise through lateral movement. This issue demonstrates the importance of comprehensive security testing for extension modules and the need for thorough validation of security controls across all components of a software platform.
The remediation approach for this vulnerability requires immediate upgrading to versions 2.35.1 or 3.0.3 of WireMock, which contain the necessary fixes to properly enforce proxy address filtering for webhook operations. For organizations unable to perform immediate upgrades, the recommended mitigation strategy involves implementing external firewall rules to define permitted destinations and restrict outbound connections from WireMock instances. This approach aligns with security best practices for network segmentation and provides a temporary solution while longer-term upgrades are planned. The discontinuation of WireMock Studio represents a significant change in the product lifecycle, leaving users with limited support options for legacy installations. Organizations should consider this vulnerability as part of their broader security posture assessment and ensure that all components of their testing and development infrastructure maintain proper security boundaries. The vulnerability serves as a reminder of the critical importance of validating security controls across all features of complex software platforms, particularly when dealing with proxy and forwarding capabilities that can potentially expose internal systems to external threats. This issue has been classified under CWE-284 for Improper Access Control and represents a failure in implementing proper authorization checks for webhook operations within the WireMock framework, highlighting the need for comprehensive security testing throughout the software development lifecycle.