Red Hat has disclosed an Important security vulnerability in the OpenShift oc-mirror tool that could allow attackers to bypass PGP signature verification and introduce malicious release images into disconnected OpenShift environments.

Tracked as CVE-2026-75939, the issue carries a CVSS v3.1 score of 7.4 and was made public on September 21, 2026. The flaw affects the openshift/oc-mirror component, which organizations use to copy OpenShift release images, operator catalogs, and related content into private registries.

This process is particularly important for air-gapped or disconnected deployments, where systems cannot download software directly from Red Hat registries or the public internet.

According to Red Hat, oc-mirror incorrectly validates PGP-signed release image signatures. The tool checks for signature errors before it has finished processing the entire signed message body.

This creates a verification bypass condition in which a specially crafted PGP message may appear trusted even though its signature is forged.

Red Hat OpenShift Flaw

An attacker would need the ability to intercept or alter traffic between the affected oc-mirror instance and the signature endpoint. They could then provide a forged PGP message that contains a valid Red Hat release key ID.

Because of the flawed validation sequence, the tool could accept the malicious message as legitimate and mirror a hostile release payload into a disconnected registry. This is a serious supply-chain risk because mirrored content is commonly treated as approved internal software.

Once a malicious release image reaches the private registry, OpenShift administrators or automated installation pipelines could select it for deployment. That could expose clusters to unauthorized code execution, application tampering, credential theft, or data access.

Red Hat rated the issue as Important and assigned it a network attack vector. The vulnerability does not require attacker privileges or user interaction.

However, exploitation has high attack complexity because the attacker must successfully manipulate signature-related network traffic. Red Hat’s CVSS vector lists high confidentiality and integrity impact, while availability impact is rated as none.

The affected component is openshift4/oc-mirror-plugin-rhel9 in Red Hat OpenShift Container Platform 4. The RHEL 8 version of the plugin is listed as not affected because the component is not present.

Red Hat noted that older package versions in affected minor product streams should generally be considered vulnerable unless explicitly marked otherwise.

At the time of disclosure, Red Hat said no practical mitigation met its standard deployment and stability criteria. Organizations using oc-mirror should therefore treat release-mirroring workflows as high risk until security errata or updated packages are issued.

Administrators should restrict network access to signature endpoints, enforce TLS inspection safeguards carefully, monitor for unusual changes in mirrored registry content, and validate release digests through independent trusted channels before promoting content into production.

Teams should also review disconnected registry access controls, audit recent mirrored releases, and watch Red Hat’s security advisories for remediation updates.

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