A Valid Red Hat Key ID Could Still Deliver a Forged OpenShift Release
A disconnected OpenShift environment is designed to reduce external dependency. A flaw in the tool that moves releases across that boundary could instead let a forged update arrive carrying a familiar Red Hat key identity.
Update, 31 October 2026: Red Hat has released a correction for the OpenShift Container Platform 4.18 branch. The 15 October advisory identifies release 4.18.57 and four corrected plugin images. Match the release channel, architecture and full image digests before promoting an import.
CVE-2026-75939 affects the RHEL 9 build of the oc-mirror plugin. Red Hat rates it Important with a CVSS 3.1 score of 7.4. The RHEL 8 plugin is listed as not affected because the component is not present.
The check happened before the signed body was finished
Red Hat says the tool checks for PGP signature errors before the entire signed body has been processed. An attacker able to intercept or manipulate traffic to the signature endpoint could craft a message containing a valid Red Hat release key ID but a forged signature.
The tool may then accept and mirror a malicious release payload into the disconnected registry. The trust signal is real, but it has been evaluated at the wrong point in the verification process.
Disconnected does not mean verification can be weaker
Air-gapped and disconnected environments often concentrate trust in a small number of import workflows. When one of those workflows accepts a release, downstream clusters may treat it as approved precisely because the environment cannot consult external services during deployment.
- Identify every system using the RHEL 9
oc-mirrorplugin and record the exact package build. - Pause unverified release imports where the vulnerable plugin remains in use.
- Protect the connected staging host and the route to the signature endpoint from interception and unauthorised modification.
- Independently verify imported release digests and signatures with a fixed tool before promotion.
- Review recently mirrored content, workflow logs and registry writes for unexpected images or altered manifests.
- Keep a reproducible chain of custody from external retrieval to disconnected registry admission.
At the original 23 September publication, the vendor record did not list an erratum. That changed with the 15 October correction detailed in the update below. Red Hat still says no temporary mitigation is available, or that available options do not meet its criteria for deployment simplicity, broad applicability and stability. Containment should not become a silent exception that permanently weakens release verification.
No exploitation is reported in Red Hat’s entry. The impact of CVE-2026-75939 comes from where it sits: at the narrow point where trusted software is admitted into an environment designed not to ask the outside world again.
Update, 31 October 2026: a fix is available for the 4.18 branch
RHSA-2026:79039, issued and updated on 15 October, provides OpenShift Container Platform 4.18.57 container images. It directs all 4.18 users to update packages and images when the correction is available in their appropriate release channel. The advisory links a separate RPM-package erratum; the image advisory is not a claim that replacing one plugin file completes every cluster upgrade step.
The vendor’s current structured record identifies four fixed oc-mirror-plugin-rhel9 images. Each pair below separates the OpenShift release image from the corrected plugin image. These are different objects, so compare the entire matching digest and architecture rather than treating a release label or a familiar signing-key identity as sufficient proof.
x86_64 / amd64
- OpenShift release image:
sha256:7a0078ddb 04d84aac e3976582 be4c7b6b 3bf095c8 e899a745 9d3c61ec 8bfe5c0 - Corrected
oc-mirror-plugin-rhel9image:sha256:578dc569b c7046692 c59c8741 31497f81 36bfe78b b78f4f97 08d35e5a 241fcab
s390x
- OpenShift release image:
sha256:73b54cac4 6826fcbc 423506e1 f35ee514 0b06060c f56ef575 0c6837e3 318c85c - Corrected
oc-mirror-plugin-rhel9image:sha256:573498057 d8a31dd1 a42a917a 71de3626 069fc471 a273c16f 60d85dcc 7230604
ppc64le
- OpenShift release image:
sha256:8b84765c9 2b6586f3 a6a37476 45484a36 738ea1c2 55101368 0c2ca85b 5919d8a - Corrected
oc-mirror-plugin-rhel9image:sha256:9b25773db cf074554 2c281d7f fceb65af fd7c0a53 bce70293 6c42360f 38a3f0a
aarch64 / arm64
- OpenShift release image:
sha256:683a1a323 2929b959 d9476b53 7e06e017 e3c4ab69 9b453a89 ac891de5 e06507d - Corrected
oc-mirror-plugin-rhel9image:sha256:d8f63b2a7 ee830e96 a4ef3275 cd31695e 5c1a674a 3ea324b1 1d86780f aa06625
The RHEL 8 plugin remains listed as not affected because the component is absent. The four fixed image entries are scoped to OpenShift Container Platform 4.18. They do not establish the remedy or support status of every other release branch. Check the matching vendor release notes and channel guidance before an upgrade.
For an affected import workflow, install the corrected packages and images, then verify release digests and signatures with a corrected verifier before promotion. Retain the original release manifest, retrieval history, verification result and registry-admission record. Network restrictions and an import pause can reduce exposure while that work is organised; they do not replace the vendor correction.
The structured record checked for this update is revision 3, generated on 15 October at 19:13:54 UTC. The disclosure and fix dates are separate events. The vendor material reviewed does not report observed exploitation, which is not proof that no attack occurred.
Sources
- Red Hat Product Security advisory. The CNA records public disclosure on 21 September 2026 at 13:27:53.361 UTC; CVE publication followed at 14:05:10.429 UTC.
- Red Hat machine-readable VEX record.
- Red Hat 4.18.57 image advisory, issued and updated 15 October 2026. Release and plugin digests checked against the current advisory and structured record.
