Red Hat oc-mirror CVE-2026-75939

Requires the attacker to occupy a man-in-the-middle / on-path position capable of intercepting or manipulating oc-mirror's network traffic to the release signature endpoint (reflected in CVSS AC:H). The victim must be actively running an oc-mirror operation that performs PGP release-image signature verification, typically in a disconnected/air-gapped OpenShift 4 registry-mirroring workflow. No authentication is needed against oc-mirror itself (PR:N) and no user interaction beyond running the normal mirror process (UI:N), but the on-path requirement and the need for an in-progress mirror operation are the practical limiting factors that keep this from being trivially exploitable.

This is a genuine cryptographic-signature-verification bypass (CWE-347) in openshift/oc-mirror, but the real-world risk is moderate and gated by a demanding attack precondition. The Red Hat CVSS 3.1 vector (AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N, 7.4) correctly encodes AC:H - the attacker must hold a man-in-the-middle position against traffic to the signature endpoint, which is the single biggest limiter. No EPSS score, no CISA KEV entry, and no public POC were supplied, so exploitation is theoretical at analysis time; there is no signal of widespread opportunistic attacks. I partially dispute the impact weighting: the vulnerability's direct effect is integrity (accepting a forged-signature release payload), so I:H is well justified, but C:H is generous - the flaw does not itself disclose data, and confidentiality/availability loss would only follow downstream from deploying a poisoned payload. Net: a real integrity-focused priority for organizations running disconnected/air-gapped OpenShift mirroring who cannot fully trust the network path to the signature endpoint, but not a drop-everything internet-wide threat given AC:H and no exploitation evidence.

An attacker who can intercept or tamper with network traffic between oc-mirror and the release signature endpoint (e.g., a compromised proxy, rogue on-path device, or DNS/TLS-stripping position) crafts a PGP message that carries a legitimate Red Hat release key ID but a forged signature. Because oc-mirror checks for signature errors before the full signed body is processed, the forged message passes verification, and the tool mirrors an attacker-controlled malicious release payload into the disconnected registry. No public exploit code was identified at time of analysis, and the network-manipulation requirement (AC:H) makes this an opportunistic-to-targeted attack rather than a trivial one.