CVE-2023-41329 in WireMock
Summary
by MITRE • 09/07/2023
WireMock is a tool for mocking HTTP services. The proxy mode of WireMock, can be protected by the network restrictions configuration, as documented in Preventing proxying to and recording from specific target addresses. These restrictions can be configured using the domain names, and in such a case the configuration is vulnerable to the DNS rebinding attacks. A similar patch was applied in WireMock 3.0.0-beta-15 for the WireMock Webhook Extensions. The root cause of the attack is a defect in the logic which allows for a race condition triggered by a DNS server whose address expires in between the initial validation and the outbound network request that might go to a domain that was supposed to be prohibited. Control over a DNS service is required to exploit this attack, so it has high execution complexity and limited impact. This issue has been addressed in version 2.35.1 of wiremock-jre8 and wiremock-jre8-standalone, version 3.0.3 of wiremock and wiremock-standalone, version 2.6.1 of the python version of wiremock, and versions 2.35.1-1 and 3.0.3-1 of the wiremock/wiremock Docker container. Users are advised to upgrade. Users unable to upgrade should either configure firewall rules to define the list of permitted destinations or to configure WireMock to use IP addresses instead of the domain names.
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Analysis
by VulDB Data Team • 10/02/2023
WireMock serves as a critical component in software testing environments for mocking HTTP services and simulating various network conditions. The vulnerability identified as CVE-2023-41329 specifically affects WireMock's proxy mode functionality, which allows the tool to forward requests to external services while maintaining the ability to record and replay responses. This proxy capability includes built-in network restrictions designed to prevent unauthorized access to specific target addresses, a security feature that becomes compromised when domain name-based restrictions are implemented. The vulnerability stems from a race condition in the DNS resolution logic that occurs between the initial validation phase and the actual outbound network request. When domain names are used for restriction configuration, the system's validation process can be bypassed if a malicious DNS server returns different IP addresses during the brief window between validation and execution, effectively allowing connections to prohibited domains that should have been blocked.
The technical flaw manifests as a DNS rebinding attack vector where an attacker controls a DNS server that can return different IP addresses for the same domain name. During the validation phase, the system resolves the domain name and checks against the configured restrictions, but when the actual network request occurs, the DNS server can return an IP address that was not present in the original validation, thus bypassing the protection mechanism. This vulnerability specifically impacts the logic that handles domain name resolution within the proxy restrictions system, creating a temporal window where the system's security posture can be circumvented. The race condition occurs because DNS responses are cached with TTL (Time To Live) values, and if a DNS server's address expires between validation and request execution, the system may proceed with a connection to an IP address that was not originally intended to be accessible.
The operational impact of this vulnerability is significant within testing and development environments where WireMock is used to simulate external services and where network isolation is crucial for security. Attackers with control over DNS servers can potentially bypass network restrictions that are meant to prevent access to internal services or sensitive endpoints. The attack requires specific conditions including control over a DNS service and knowledge of the target system's configuration, making the execution complexity high but not impossible. The vulnerability affects multiple versions of WireMock across different implementations including Java, Python, and Docker containers, indicating a widespread impact across various deployment scenarios. Organizations using WireMock in proxy mode with domain-based restrictions are at risk, particularly those that rely on this feature for network segmentation and security isolation.
Security controls should be implemented to address this vulnerability through proper upgrade management and configuration hardening. The patched versions of WireMock address this issue by improving the DNS resolution logic to ensure consistent validation throughout the request lifecycle, preventing the race condition that enables the attack. Organizations should immediately upgrade to the patched versions including wiremock-jre8 2.35.1, wiremock 3.0.3, python version 2.6.1, and the corresponding Docker container versions. When upgrading is not immediately possible, organizations should implement firewall rules to explicitly define permitted destinations, effectively creating network-level controls outside the application's built-in restrictions. Alternative mitigation strategies include configuring WireMock to use IP addresses instead of domain names for restriction configuration, which eliminates the DNS resolution timing issues that enable this attack vector. This vulnerability aligns with CWE-345 Insufficient Verification of Data Authenticity, as the system fails to properly validate the consistency of DNS responses throughout the request lifecycle, and relates to ATT&CK technique T1071.004 Application Layer Protocol: DNS, which covers the use of DNS for command and control activities and privilege escalation techniques. The vulnerability demonstrates the importance of considering DNS security implications in application-level network controls and highlights the need for comprehensive validation of network access controls in distributed systems.