# CVE-2026-126068: Action Mailbox: Possible signature replay in Action Mailbox Mailgun ingress


- **Severity:** Low 3.7 (`CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:L/A:N`)
- **Exploited in the wild:** Not known
- **Fix available:** Yes
- **Published:** 10 Nov 2026
- **Updated:** 10 Nov 2026
- **Also known as:** DEBIAN-CVE-2026-126068, GHSA-5957-c7qm-m469, UBUNTU-CVE-2026-126068

## 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 (Authentication Bypass by Capture-replay)

## Which versions are affected by CVE-2026-126068?

2 open source packages ship an affected version, including actionmailbox.


| Package | Ecosystem | 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.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-126068 and fix it if it is affected.

What it is: CVE-2026-126068 is a low-severity vulnerability in rails, published on 10 Nov 2026. 
Exploitation: There is no known exploitation of CVE-2026-126068 in the wild and no public exploit code.

Affected packages and fixed versions:
- actionmailbox (RubyGems): affected all versions; fixed in 8.0.5.2
- actionmailbox (RubyGems): affected from 8.1.0.beta1; fixed in 8.1.4.1

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-126068/ (Markdown: https://insights.sbomify.com/CVE-2026-126068/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-126068
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-126068
- OSV: https://osv.dev/vulnerability/CVE-2026-126068

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-126068/
Summaries are generated and may contain mistakes; the official description above is the record.