CVE-2026-56742

Analyzed Analyzed - Analysis Complete

Authorization Bypass in Cilium Gateway API

Publication date: 2026-07-15

Last updated on: 2026-07-17

Assigner: GitHub, Inc.

Description

Cilium is a networking, observability, and security solution. Prior to 1.17.17, 1.18.11, and 1.19.5, Cilium clusters using Gateway API allow users with permissions to create or update namespaced HTTPRoutes to mirror HTTP traffic to any Service in any namespace, bypassing the ReferenceGrant authorization mechanism. Gateway API functionality is disabled by default. This issue is fixed in versions 1.17.17, 1.18.11, and 1.19.5.

CVSS Scores

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Meta Information

Published

2026-07-15

Last Modified

2026-07-17

Generated

2026-08-05

AI Q&A

2026-07-16

EPSS Evaluated

2026-08-03

NVD

CVE-2026-56742

EUVD

EUVD-2026-44773

Affected Vendors & Products

Vendor	Product	Version / Range
cilium	cilium	to 1.17.17 (exc)
cilium	cilium	From 1.18.0 (inc) to 1.18.11 (exc)
cilium	cilium	From 1.19.0 (inc) to 1.19.5 (exc)

Helpful Resources

Exploitability

CWE

KEV

CWE ID	Description
CWE-862	The product does not perform an authorization check when an actor attempts to access a resource or perform an action.

Attack-Flow Graph

Executive Summary

CVE-2026-56742 is a vulnerability in Cilium affecting versions before 1.17.17, 1.18.10, and 1.19.4. It involves namespaced HTTPRoutes in clusters using Gateway API where users with permissions to create or update these routes can redirect HTTP traffic to any Service in any namespace, bypassing the ReferenceGrant authorization mechanism.

Detection Guidance

To detect this vulnerability, check if your Cilium version is below 1.17.17, 1.18.11, or 1.19.5. Run: cilium version. If using Gateway API, verify HTTPRoute objects for unauthorized cross-namespace backend references. Inspect logs for request-mirror filter usage without proper ReferenceGrant validation.

Impact Analysis

An attacker with permissions to create or update namespaced HTTPRoutes could exploit this to redirect traffic to unauthorized services, potentially leading to data leaks, service disruption, or unauthorized access to sensitive information across namespaces.

Compliance Impact

This vulnerability could lead to unauthorized data access or exfiltration, violating data protection requirements in GDPR and HIPAA. It undermines access control mechanisms, potentially resulting in non-compliance with these regulations.

Mitigation Strategies

Upgrade Cilium to versions 1.17.17, 1.18.11, or 1.19.5 or later to patch the vulnerability.
Restrict permissions for creating or updating namespaced HTTPRoutes to cluster admins only.
Verify that ReferenceGrant authorization mechanisms are properly enforced for cross-namespace access.

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