CVE-2026-23990

MEDIUM EPSS 22.0%
Published Jan 21, 20265mo ago · Modified Jun 17, 20262w ago
5.3 CVSS 3.1
Medium
Find Similar
Published Jan 21, 2026 5mo ago
Last Modified Jun 17, 2026 2w ago

Description

The Flux Operator is a Kubernetes CRD controller that manages the lifecycle of CNCF Flux CD and the ControlPlane enterprise distribution. Starting in version 0.36.0 and prior to version 0.40.0, a privilege escalation vulnerability exists in the Flux Operator Web UI authentication code that allows an attacker to bypass Kubernetes RBAC impersonation and execute API requests with the operator's service account privileges. In order to be vulnerable, cluster admins must configure the Flux Operator with an OIDC provider that issues tokens lacking the expected claims (e.g., `email`, `groups`), or configure custom CEL expressions that can evaluate to empty values. After OIDC token claims are processed through CEL expressions, there is no validation that the resulting `username` and `groups` values are non-empty. When both values are empty, the Kubernetes client-go library does not add impersonation headers to API requests, causing them to be executed with the flux-operator service account's credentials instead of the authenticated user's limited permissions. This can result in privilege escalation, data exposure, and/or information disclosure. Version 0.40.0 patches the issue.

CVSS Details

Base Score
5.3
Exploitability
1.6
Impact
3.6
Vector string
CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:H/I:N/A:N
Attack Vector Network
Attack Complexity High
Privileges Required Low
User Interaction None
Scope Unchanged
Confidentiality High
Integrity None
Availability None

Threat Intelligence

EPSS Exploit Probability
22.0% percentile
Exploit & Patch Status
No Known Exploit
Patch Available

Weaknesses 2

CWE-269 Improper Privilege Management Authorization
CWE-862 Missing Authorization Authorization

Affected Products 1

VendorProductVersionRange
control-planeflux_operator*≥0.36.0  –  <0.40.0

References 4

  • github.com https://github.com/controlplaneio-fluxcd/flux-operator/commit/084540424f6de8ba5d88fb1fd1e8472ba29afd7e
    Patch
  • github.com https://github.com/controlplaneio-fluxcd/flux-operator/pull/610
    Issue TrackingPatch
  • github.com https://github.com/controlplaneio-fluxcd/flux-operator/releases/tag/v0.40.0
    ProductRelease Notes
  • github.com https://github.com/controlplaneio-fluxcd/flux-operator/security/advisories/GHSA-4xh5-jcj2-ch8q
    MitigationVendor Advisory

Remediation

  • github.com https://github.com/controlplaneio-fluxcd/flux-operator/commit/084540424f6de8ba5d88fb1fd1e8472ba29afd7e
    Patch
  • github.com https://github.com/controlplaneio-fluxcd/flux-operator/pull/610
    Issue TrackingPatch