Potential network policy bypass when routing IPv6 traffic

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS

4.2 · CVSS:3.1/AV:A/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:N

EPSS

• CVE-2023-27594: 0.55% estimated exploitation activity in the next 30 days; percentile 46.20 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.

As published by the source; long descriptions are shortened.

Impact Under specific conditions, Cilium may misattribute the source IP address of traffic to a cluster, identifying external traffic as coming from the host on which Cilium is running. As a consequence, network policies for that cluster might be bypassed, depending on the specific network policies enabled. Only IPv6 traffic is impacted by this vulnerability. This issue only manifests when: Cilium is routing IPv6 traffic, and Kube-proxy is used for service handling, and NodePorts are used to route traffic to pods. IPv6 is disabled by default. Cilium's kube-proxy replacement feature is not affected by this vulnerability. Patches The problem has been fixed and is available on versions =1.11.15, =1.12.8, =1.13.1 Workarounds Disable IPv6 routing (IPv6 is disabled by default). Acknowledgements The Cilium community has worked together with members of Isovalent to prepare these mitigations. Special thanks to Yusuke Suzuki for both highlighting and fixing the issue. For more information If…

Published by the source

17 Mar 2023, 18:22 UTC

Last modified by the source

24 Mar 2023, 21:41 UTC

Source last checked

26 Oct 2026, 14:55 UTC

1. Revision 1 · created · 26 Oct 2026

   Published from ghsa record GHSA-8fg8-jh2h-f2hc

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# Patch Next advisory brief: CVE-2023-27594

Advisory: Potential network policy bypass when routing IPv6 traffic
IDs: CVE-2023-27594, GHSA-8fg8-jh2h-f2hc
Record: https://patchnext.com/advisories/cve-2023-27594 (revision 1, source checked 26 Oct 2026, 14:55 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: Medium (CVSS 4.2)
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 1.13.1, 1.12.8, 1.11.15. A vendor fix does not mean a deployment is fixed.

## Affected components
- Go github.com/cilium/cilium: affected < 1.11.15; >= 1.12.0, < 1.12.8; >= 1.13.0, < 1.13.1; fixed in 1.12.8, 1.13.1, 1.11.15

## Suggested inspection (read-only)
- Go github.com/cilium/cilium: 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.
- 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://github.com/advisories/GHSA-8fg8-jh2h-f2hc (GitHub-reviewed advisory GHSA-8fg8-jh2h-f2hc lists affected ranges: Go github.com/cilium/cilium >=0 =1.12.0 =1.13.0 <1.13.1)

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