CVE-2026-66787
MEDIUMDescription
A flaw was found in the lighthouse component of Red Hat Advanced Cluster Management for Kubernetes. This vulnerability stems from insufficient validation of advertised IP addresses within EndpointSlice objects. A compromised spoke cluster can exploit this by creating EndpointSlices with attacker-controlled IP addresses, causing other clusters' lighthouse DNS to redirect legitimate service traffic to malicious endpoints. This enables a remote attacker to conduct transparent Man-in-the-Middle (MITM) attacks on cross-cluster service communications, potentially leading to unauthorized information disclosure and data manipulation.
How to fix
This vulnerability affects an unusually large number of packages. The highest-confidence fixes are shown above; the full list is longer. Check the referenced advisories for complete coverage.
TridentStack Control can deploy fixes like this automatically across your Windows, macOS, and Linux fleet. See how it works
Remediation is compiled from vendor and distribution security advisories. Always confirm against the linked source for your exact version and platform.
CVSS v3 Vector
Exploitability
Impact
CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:L
Exploit Intelligence
Low risk: more likely to be exploited than 15% of all known CVEs.
References
Related Vulnerabilities
Other CWE-489 vulnerabilities, ordered by exploit likelihood. View all
| CVE | Severity | CVSS | EPSS | Exploited | Fix |
|---|---|---|---|---|---|
| CVE-2023-32645 | Critical | 9.8 | 54% | - | - |
| CVE-2017-5259 | High | 8.8 | 31% | - | - |
| CVE-2022-20649 | High | 8.1 | 12% | - | - |
| CVE-2022-38715 | High | 8.8 | 3.7% | - | - |
| CVE-2018-5454 | High | 8.1 | 3.4% | - | - |
| CVE-2024-9643 | Critical | 9.8 | 3.0% | - | - |
Common questions
How do I fix CVE-2026-66787?
Published advisories record a fix for 10 affected products. The "How to fix" section on this page lists the fixed version and source advisory for each one, so apply the entry matching what you actually run.
Is CVE-2026-66787 being actively exploited?
Not that we know of. CVE-2026-66787 is not in the CISA Known Exploited Vulnerabilities catalog. Its EPSS score of 0.24% is the estimated probability that it will be exploited in the next 30 days. That is higher than 15% of all scored CVEs.
How severe is CVE-2026-66787?
CVE-2026-66787 has a CVSS v3 base score of 5.4, rated medium. CVSS rates the technical impact if the vulnerability is exploited, not how likely that is, so weigh it alongside the exploit-prediction score when you decide what to patch first.
What does CVE-2026-66787 affect?
Published advisories record a fix for registry.redhat.io/rhacm2/lighthouse (Red Hat / RHEL), registry.redhat.io/rhacm2/lighthouse (Rocky), registry.redhat.io/rhacm2/nettest (Rocky), registry.redhat.io/rhacm2/nettest (Red Hat / RHEL), and 6 more. Only products with a sourced advisory are listed, so treat this as what we can cite rather than a complete inventory.
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This product uses NVD data but is not endorsed or certified by the NVD. EPSS scores courtesy of FIRST.org (https://www.first.org/epss). Source: CISA KEV Catalog. Data as of 2026-09-03.