ExternalName Services can be used to gain access to Envoy's admin interface

Exploitation

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

CVSS

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

EPSS

• CVE-2021-32783: 1.15% estimated exploitation activity in the next 30 days; percentile 66.95 (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 Josh Ferrell (@josh-ferrell) from VMware has reported that a specially crafted ExternalName type Service may be used to access Envoy's admin interface, which Contour normally prevents from access outside the Envoy container. This can be used to shut down Envoy remotely (a denial of service), or to expose the existence of any Secret that Envoy is using for its configuration, including most notably TLS Keypairs. However, it cannot be used to get the content of those secrets. Since this attack allows access to the administration interface, a variety of administration options are available, such as shutting down the Envoy or draining traffic. In general, the Envoy admin interface cannot easily be used for making changes to the cluster, in-flight requests, or backend services, but it could be used to shut down or drain Envoy, change traffic routing, or to retrieve secret metadata, as mentioned above. Patches The issue will be addressed in the forthcoming Contour v1.18.0 and a patch…

Published by the source

30 Aug 2021, 17:22 UTC

Last modified by the source

1 Feb 2023, 05:06 UTC

Source last checked

26 Oct 2026, 14:54 UTC

1. Revision 1 · created · 26 Oct 2026

   Published from ghsa record GHSA-5ph6-qq5x-7jwc

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# Patch Next advisory brief: CVE-2021-32783

Advisory: ExternalName Services can be used to gain access to Envoy's admin interface
IDs: CVE-2021-32783, GHSA-5ph6-qq5x-7jwc
Record: https://patchnext.com/advisories/cve-2021-32783 (revision 1, source checked 26 Oct 2026, 14:54 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: High (CVSS 8.5)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: github.com/projectcontour/contour 1.17.1, 1.16.1, 1.15.2, 1.14.2. A vendor fix does not mean a deployment is fixed.

## Affected components
- Go github.com/projectcontour/contour: affected < 1.14.2; >= 1.15.0, < 1.15.2; >= 1.16.0, <= 1.16.0; >= 1.17.0, <= 1.17.0; fixed in 1.14.2, 1.17.1, 1.16.1, 1.15.2

## Suggested inspection (read-only)
- Go github.com/projectcontour/contour: 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/projectcontour/contour.
- 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-5ph6-qq5x-7jwc (GitHub-reviewed advisory GHSA-5ph6-qq5x-7jwc lists affected ranges: Go github.com/projectcontour/contour >=0 =1.15.0 =1.16.0 =1.17.0 <=1.17.0)

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