Vulnerability record · CVE-2021-32783 · published 23 July 2021
CVE-2021-32783: Projectcontour contour vulnerability
Projectcontour · Contour
Contour is a Kubernetes ingress controller using Envoy proxy. In Contour before version 1.17.1 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. The issue will be addressed in Contour v1.18.0 and a cherry-picked patch release, v1.17.1, has been released to cover users who cannot upgrade at this time. For more details refer to the linked GitHub Security Advisory.
Description
Contour is a Kubernetes ingress controller using Envoy proxy. In Contour before version 1.17.1 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. The issue will be addressed in Contour v1.18.0 and a cherry-picked patch release, v1.17.1, has been released to cover users who cannot upgrade at this time. For more details refer to the linked GitHub Security Advisory.
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:L/I:N/A:H
Affected products
1 vulnerable configurations from NVD's CPE data, grouped by vendor and product.
References
| Link | Tags |
|---|---|
| https://github.com/projectcontour/contour/commit/b53a5c4fd927f4ea2c6cf02f1359d8e28bef852e | PatchThird Party Advisory |
| https://github.com/projectcontour/contour/releases/tag/v1.17.1 | Release NotesThird Party Advisory |
| https://github.com/projectcontour/contour/security/advisories/GHSA-5ph6-qq5x-7jwc | Third Party Advisory |
| https://github.com/projectcontour/contour/commit/b53a5c4fd927f4ea2c6cf02f1359d8e28bef852e | PatchThird Party Advisory |
| https://github.com/projectcontour/contour/releases/tag/v1.17.1 | Release NotesThird Party Advisory |
| https://github.com/projectcontour/contour/security/advisories/GHSA-5ph6-qq5x-7jwc | Third Party Advisory |
Track CVE-2021-32783 inside VULONE
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Related vulnerabilities
Same products first, then exploited flaws of the same weakness class.
Source: NIST National Vulnerability Database (record CVE-2021-32783), CISA KEV, FIRST EPSS (scores of 2026-09-27). This page is refreshed as NVD updates the record.
