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Fencer Vulns
high 8.5

CVE-2021-32783 json

Authorization bypass in Contour

published 2021-07-23 5 y ago modified 2026-09-08 2 mo ago also BIT-contour-2021-32783 , EUVD-2021-1578 , GHSA-5ph6-qq5x-7jwc , GO-2022-0922

cvss
8.5
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
1.2%
EPSS 1.2% chance of exploitation in 30 days, percentile 67%
public exploits
0
none known

Summary

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.

Patch / fix

  • go github.com/projectcontour/contour 1.14.2, 1.15.2, 1.16.1, 1.17.1
  • bitnami contour 1.17.1
  • projectcontour contour 1.17.1

Exploit prediction

1.15% chance of exploitation in the next 30 days, higher than 67% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by version score vector
CNA 3.1 8.5 CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:L/I:N/A:H
GitHub 3.1 8.5 CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:L/I:N/A:H
NVD 3.1 8.5 CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:L/I:N/A:H
NVD 2.0 5.5 AV:N/AC:L/Au:S/C:P/I:N/A:P
OSV 3.1 8.5 CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:L/I:N/A:H

Affected packages

ecosystem package affected fixed in
go github.com/projectcontour/contour
<1.14.2
>=1.15.0, <1.15.2
>=1.16.0, <1.16.1
>=1.17.0, <1.17.1
1.14.2
1.15.2
1.16.1
1.17.1
bitnami contour
<1.17.1
1.17.1

Affected products

  • projectcontour contour

Classification

Weakness
  • CWE-441 Unintended Proxy or Intermediary
  • CWE-610 Externally Controlled Reference to a Resource in Another Sphere

References

Sources

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.