CVE-2026-126068 Action Mailbox: Possible signature replay in Action Mailbox Mailgun ingress
- Exploited in the wild
- Not known
- Fix
- Available
What is CVE-2026-126068?
CVE-2026-126068 is a low-severity vulnerability in rails, published on 10 Nov 2026.
Official description
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.
Weakness: CWE-294
Which versions are affected by CVE-2026-126068?
2 open source packages ship an affected version, including actionmailbox.
| Package | Affected | Fixed in |
|---|---|---|
actionmailbox RubyGems | All versions | 8.0.5.2 |
actionmailbox RubyGems | From 8.1.0.beta1 | 8.1.4.1 |
How do I fix CVE-2026-126068?
Upgrade actionmailbox to a fixed version for your release line: 8.0.5.2 or 8.1.4.1.
Is CVE-2026-126068 being exploited?
There is no known exploitation of CVE-2026-126068 in the wild and no public exploit code.
Sources
Also known as DEBIAN-CVE-2026-126068, GHSA-5957-c7qm-m469, UBUNTU-CVE-2026-126068.