Domain restrictions bypass via DNS Rebinding in WireMock and WireMock Studio webhooks, proxy and recorder modes

QFinch assessment

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](https://wiremock.org/docs/configuration/#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.

Potential impact

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.