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Fencer Vulns
high 7.4

CVE-2022-21656 json

X.509 subjectAltName matching bypass in Envoy

published 2022-02-22 4 y ago modified 2026-09-10 59 d ago also BIT-envoy-2022-21656 , EUVD-2022-26874 , GHSA-c9g7-xwcv-pjx2

cvss
7.4
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
0.7%
EPSS 0.7% chance of exploitation in 30 days, percentile 52%
public exploits
0
none known

Summary

Envoy is an open source edge and service proxy, designed for cloud-native applications. The default_validator.cc implementation used to implement the default certificate validation routines has a "type confusion" bug when processing subjectAltNames. This processing allows, for example, an rfc822Name or uniformResourceIndicator to be authenticated as a domain name. This confusion allows for the bypassing of nameConstraints, as processed by the underlying OpenSSL/BoringSSL implementation, exposing the possibility of impersonation of arbitrary servers. As a result Envoy will trust upstream certificates that should not be trusted.

Patch / fix

  • bitnami envoy 1.20.2
  • envoyproxy envoy 1.20.2

Vendor advisories

What the vendors themselves say about their products: affected, fixed or not affected, and what to do.

red hat product security vex CVE-2022-21656 updated cvss 5.9

envoy: X.509 subjectAltName matching (and nameConstraints) bypass

  • Red Hat OpenShift Service Mesh 2.0 servicemesh-proxy
    affected: no fix available
  • Red Hat OpenShift Service Mesh 2.1 servicemesh-proxy, servicemesh-proxy-wasm
    affected: no fix planned “Will not fix”
  • Red Hat OpenShift Service Mesh 2 openshift-service-mesh/proxyv2-rhel8
    not affected: vulnerable code not present

Red Hat CSAF VEX © Red Hat, Inc., from https://security.access.redhat.com/data/csaf/v2/vex/; changed: reduced to product statuses and remediations. CC BY 4.0 · csaf

CISA SSVC

Exploitation
none
Automatable
no
Technical impact
total
Assessed
18 mo ago

Exploit prediction

0.67% chance of exploitation in the next 30 days, higher than 52% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by version score vector
CNA 3.1 7.4 CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N
NVD 3.1 5.9 CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:H/A:N
NVD 2.0 5.8 AV:N/AC:M/Au:N/C:P/I:P/A:N
OSV 3.1 7.4 CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N

Affected packages

ecosystem package affected fixed in
bitnami envoy
<1.20.2
1.20.2

Affected products

  • envoyproxy envoy

Classification

Weakness
  • CWE-295 Improper Certificate Validation
  • CWE-843 Access of Resource Using Incompatible Type

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.