Rails prior 8.0.5.2/8.1.4.1 Mailgun Ingress Authenticator#recent timestamp/token signature verification

Summaryinfo

A vulnerability was found in Rails. It has been declared as problematic. This issue affects the function ActionMailbox::Ingresses::Mailgun::InboundEmailsController::Authenticator#recent of the component Mailgun Ingress. The manipulation of the argument timestamp/token results in signature verification. This vulnerability is known as CVE-2026-126068. It is possible to launch the attack remotely. No exploit is available. It is recommended to upgrade the affected component.

Detailsinfo

A vulnerability classified as problematic has been found in Rails. Affected is the function ActionMailbox::Ingresses::Mailgun::InboundEmailsController::Authenticator#recent of the component Mailgun Ingress. The manipulation of the argument timestamp/token with an unknown input leads to a signature verification vulnerability. CWE is classifying the issue as CWE-347. The product does not verify, or incorrectly verifies, the cryptographic signature for data. This is going to have an impact on integrity. CVE summarizes:

Action Mailbox routes incoming emails to controller-like mailboxes for processing in Rails. Prior to 8.1.4.1 and 8.0.5.2, the Action Mailbox Mailgun ingress authenticates a request with an HMAC of the timestamp and token parameters concatenated without a separator, and ActionMailbox::Ingresses::Mailgun::InboundEmailsController::Authenticator#recent? rejects only timestamps more than 2 minutes in the past. Because the signature does not fix the boundary between the two values, a captured signed request can be presented with a timestamp far in the future, which the ingress then accepts indefinitely. An attacker who obtains one signed Mailgun webhook request, but not the signing key, could submit arbitrary inbound email that Action Mailbox processes as genuine, possibly leading to forged messages attributed to the sender of the attacker's choosing. Applications that receive inbound email through the Action Mailbox Mailgun ingress are affected. This issue is fixed in versions 8.1.4.1 and 8.0.5.2.

The advisory is available at github.com. This vulnerability is traded as CVE-2026-126068 since 11/10/2026. The exploitability is told to be easy. It is possible to launch the attack remotely. The exploitation doesn't require any form of authentication. Technical details are known, but there is no available exploit.

Upgrading to version 8.0.5.2 or 8.1.4.1 eliminates this vulnerability.

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• Rails

Website

• Product: https://github.com/rails/rails/

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