Skip to content
Patch Next
Sign inAdd to your agent

← Actionable
Medium, CVSS 5.9amended

Cilium: Namespaced HTTPRoutes can redirect traffic to other namespaces

CVE-2026-56742GHSA-w7c2-w76w-5hmj

What to do

Vendor fix available. Upgrade each affected package to the fixed version on its release line (github.com/cilium/cilium 1.19.5, 1.17.17; github.com/cilium/ciliumCilium 1.18.11), redeploy, then verify what is actually installed.

This page has no inventory attached, so it cannot say whether you are affected. A vendor fix is not proof that your deployment is fixed.

Add to your agent

Affected packages

Sources

Severity and exploitation
Exploitation
No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.
CVSS
5.9 · CVSS:3.1/AV:A/AC:L/PR:H/UI:N/S:C/C:L/I:L/A:L
EPSS
  • CVE-2026-56742: 0.18% estimated exploitation activity in the next 30 days; percentile 7.10 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.
Source description

As published by the source; long descriptions are shortened.

Impact In Cilium clusters using Gateway API, users with permissions to create or update namespaced HTTPRoutes can mirror HTTP traffic to any Service in any namespace, bypassing the ReferenceGrant authorization mechanism. Gateway API functionality is disabled by default. Patches This issue affects: Cilium v1.19 from v1.19.0 to v1.19.4 inclusive Cilium v1.18 from v1.18.0 to v1.18.10 inclusive All versions of Cilium before v1.17.17 This issue is patched in: Cilium v1.19.5 Cilium v1.18.11 Cilium v1.17.17 Workarounds There is no workaround to this issue. Users of this feature who are unable to upgrade can mitigate the risk by ensuring that RBAC permissions to create HTTPRoute objects are only granted to cluster admins. Acknowledgements The Cilium community has worked together with members of Isovalent to prepare these mitigations. Special thanks to @galanko for reporting the issue and @mhofstetter for their work on triaging and remediating this issue. For more information If you have any…

Dates and revisions
Published by the source
Last modified by the source
Source last checked
  1. Revision 3 · amended ·

    Amended from ghsa record GHSA-w7c2-w76w-5hmj

  2. Revision 2 · amended ·

    Amended from osv record GO-2026-6596

  3. Revision 1 · created ·

    Published from osv record GHSA-w7c2-w76w-5hmj

Agent brief

Preview the exact text before you copy it. Commands are read-only suggestions; review them before running anything.

# Patch Next advisory brief: CVE-2026-56742

Advisory: Cilium: Namespaced HTTPRoutes can redirect traffic to other namespaces
IDs: CVE-2026-56742, GHSA-w7c2-w76w-5hmj
Record: https://patchnext.com/advisories/cve-2026-56742 (revision 3, source checked 26 Oct 2026, 15:29 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: Medium (CVSS 5.9)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: github.com/cilium/cilium 1.19.5, 1.17.17; github.com/cilium/ciliumCilium 1.18.11. A vendor fix does not mean a deployment is fixed.

## Affected components
- Go github.com/cilium/cilium: affected < 1.17.17; >= 1.19.0, < 1.19.5; fixed in 1.17.17, 1.19.5
- Go github.com/cilium/ciliumCilium: affected >= 1.18.0, < 1.18.11; fixed in 1.18.11

## Suggested inspection (read-only)
- Go github.com/cilium/cilium: check the installed version with your package manager.
- Go github.com/cilium/ciliumCilium: check the installed version with your package manager.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on github.com/cilium/cilium, github.com/cilium/ciliumCilium.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://osv.dev/vulnerability/GO-2026-6596 (OSV record GO-2026-6596 lists affected ranges: Go github.com/cilium/cilium >=0 =1.18.0 =1.19.0 <1.19.5 (fixed))
- Verified: https://osv.dev/vulnerability/GHSA-w7c2-w76w-5hmj (OSV record GHSA-w7c2-w76w-5hmj lists affected ranges: Go github.com/cilium/cilium >=0 =1.19.0 =1.18.0 <1.18.11 (fixed))
- Verified: https://github.com/advisories/GHSA-w7c2-w76w-5hmj (GitHub-reviewed advisory GHSA-w7c2-w76w-5hmj lists affected ranges: Go github.com/cilium/cilium >=0 =1.19.0 =1.18.0 <1.18.11)

Commands are suggestions: review each one before running it.

Loading voting…