Cilium eBPF filters may be temporarily removed during agent restart

Exploitation

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

CVSS

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

EPSS

• CVE-2023-27595: 0.73% estimated exploitation activity in the next 30 days; percentile 54.45 (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 When Cilium is started, there is a short period when Cilium eBPF programs are not attached to the host. During this period, the host does not implement any of Cilium's featureset. This can cause disruption to newly established connections during this period due to the lack of Load Balancing, or can cause Network Policy bypass due to the lack of Network Policy enforcement during the window. This vulnerability impacts any Cilium-managed endpoints on the node (such as Kubernetes Pods), as well as the host network namespace (including Host Firewall). Patches This vulnerability is fixed by https://github.com/cilium/cilium/pull/24336, included in Cilium 1.13.1 or later. Cilium releases 1.12.x, 1.11.x and earlier are not affected. Workarounds There are no known workarounds. Acknowledgements The Cilium community has worked together with members of Isovalent to prepare these mitigations. Special thanks to Louis DeLosSantos and Timo Beckers for investigating and fixing the issue. For…

Published by the source

17 Mar 2023, 18:22 UTC

Last modified by the source

7 Jun 2023, 16:37 UTC

Source last checked

26 Oct 2026, 14:58 UTC

1. Revision 1 · created · 26 Oct 2026

   Published from ghsa record GHSA-r5x6-w42p-jhpp

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# Patch Next advisory brief: CVE-2023-27595

Advisory: Cilium eBPF filters may be temporarily removed during agent restart
IDs: CVE-2023-27595, GHSA-r5x6-w42p-jhpp
Record: https://patchnext.com/advisories/cve-2023-27595 (revision 1, source checked 26 Oct 2026, 14:58 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: Medium (CVSS 6.5)
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. A vendor fix does not mean a deployment is fixed.

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

## 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-r5x6-w42p-jhpp (GitHub-reviewed advisory GHSA-r5x6-w42p-jhpp lists affected ranges: Go github.com/cilium/cilium >=1.13.0 <1.13.1)

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