CVE-2026-66787
Description
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.
Statement
This Important vulnerability in Red Hat Advanced Cluster Management for Kubernetes allows a compromised spoke cluster to perform cross-cluster DNS spoofing. By creating unvalidated EndpointSlice objects with attacker-controlled IP addresses, a malicious actor can redirect legitimate service traffic between clusters, enabling transparent Man-in-the-Middle attacks without altering the target service.
Mitigation
Mitigation for this issue is either not available or the currently available options do not meet the Red Hat Product Security criteria comprising ease of use and deployment, applicability to widespread installation base, or stability.
Common Vulnerability Scoring System (CVSS) Score Details
Info alert:Important note
CVSS scores for open source components depend on vendor-specific factors (e.g. version or build chain). Therefore, Red Hat's score and impact rating can be different from NVD and other vendors. Red Hat remains the authoritative CVE Naming Authority (CNA) source for its products and services (see Red Hat classifications).
CVSS v3 Score Breakdown
| Red Hat | NVD | cve.org | |
|---|---|---|---|
| Base Score | 5.4 | N/A | 5.4 |
| Attack Vector | Adjacent Network | N/A | Adjacent Network |
| Attack Complexity | Low | N/A | Low |
| Privileges Required | None | N/A | None |
| User Interaction | None | N/A | None |
| Scope | Unchanged | N/A | Unchanged |
| Confidentiality | Low | N/A | Low |
| Integrity Impact | None | N/A | None |
| Availability Impact | Low | N/A | Low |
Vector
Red Hat: CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:L
cve.org: CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:L
Red Hat CVSS v3 Score Explanation
Reconciled from source finding FIND-001 (migration 2026-09-01)
Understanding the Weakness (CWE)
Confidentiality,Integrity,Availability,Access Control,Other
Technical Impact: Bypass Protection Mechanism; Read Application Data; Gain Privileges or Assume Identity; Varies by Context
Active debug code can create unintended entry points or expose sensitive information. The severity of the exposed debug code will depend on the particular instance. At the least, it will give an attacker sensitive information about the settings and mechanics of web applications on the server. At worst, as is often the case, the debug code will allow an attacker complete control over the web application and server, as well as confidential information that either of these access.
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