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Fencer Vulns
medium 5.5

CVE-2021-4235 json

Denial of service in gopkg.in/yaml.v2

published 2021-04-14 5 y ago modified 2026-09-10 1 mo ago also GHSA-r88r-gmrh-7j83 , GO-2021-0061 , EUVD-2022-7731

cvss
5.5
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
0.4%
EPSS 0.4% chance of exploitation in 30 days, percentile 37%
public exploits
0
none known

Summary

Due to unbounded alias chasing, a maliciously crafted YAML file can cause the system to consume significant system resources. If parsing user input, this may be used as a denial of service vector.

Patch / fix

  • go gopkg.in/yaml.v2 2.2.3
  • gopkg.in/yaml.v2 gopkg.in/yaml.v2 2.2.3
  • golang-yaml.v2 Debian 14, Debian 13, Debian 12 2.2.8-1

debian advisories DEBIAN-CVE-2021-4235

  • golang-yaml.v2 Ubuntu 20.04 LTS 2.2.2-1ubuntu0.1
  • golang-yaml.v2 Ubuntu Pro 16.04 LTS 0.0+git20160301.0.a83829b-1ubuntu0.1~esm1
  • golang-yaml.v2 Ubuntu Pro 18.04 LTS 0.0+git20170407.0.cd8b52f-1ubuntu2+esm1

ubuntu advisories UBUNTU-CVE-2021-4235

Ubuntu security data © Canonical Ltd., from https://github.com/canonical/ubuntu-security-notices via OSV; changed: normalised to fixed package versions per release. CC BY-SA 4.0

  • tox openshift ironic 4.12 3.23.0-2.el9.1
  • crit openshift 4.12 3.15-4.rhaos4.11.el8
  • criu openshift 4.12 3.15-4.rhaos4.11.el8
  • crun openshift 4.12 1.4.2-1.rhaos4.11.el8
  • crun openshift 4.12 1.4.2-2.rhaos4.12.el9
  • grpc openshift 4.12 1.18.0-4.el8ost
  • runc openshift 4.12 3:1.1.2-2.rhaos4.12.el8
  • tini openshift 4.12 0.16.1-1.el8ar

red hat advisories RHSA-2022:7398

  • podman Azure Linux 3.0 5.6.1-2
  • buildah Azure Linux 3.0 1.41.4-2

azure linux advisories AZL-45237AZL-45360

Azure Linux vulnerability data, Copyright (c) Microsoft Corporation, from https://github.com/microsoft/AzureLinuxVulnerabilityData via OSV, under the MIT licence; changed: normalised to fixed package versions per release. MIT

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-2021-4235 updated cvss 5.5

go-yaml: Denial of Service in go-yaml

  • Red Hat cert-manager Operator for Red Hat OpenShift cert-manager/jetstack-cert-manager-rhel9 Red Hat Migration Toolkit for Containers rhmtc/openshift-migration-controller-rhel8
    affected: no fix planned “Will not fix”
  • Red Hat OpenShift Developer Tools and Services odo
    affected: no fix available
  • Red Hat OpenShift Pipelines openshift-pipelines-client Red Hat OpenShift Serverless openshift-serverless-clients, openshift-serverless-1/kn-client-kn-rhel9, openshift-serverless-1/kn-client-cli-artifacts-rhel9 Red Hat Advanced Cluster Security 3 advanced-cluster-security/rhacs-main-rhel8
    affected: no fix planned “Will not fix”
  • Red Hat Ansible Automation Platform 2 openshift-clients
    affected: no fix available
  • Red Hat OpenShift Container Platform 4 openshift4/ose-tests, openshift4/ose-console, openshift4/ose-hypershift-rhel8, openshift4/ose-olm-rukpak-rhel8, openshift4/oc-mirror-plugin-rhel9, openshift4/ose-machine-api-operator, +14 more
    affected: no fix available, no fix planned “Will not fix”
  • Red Hat Openshift Container Storage 4 ocs4/cephcsi-rhel8, ocs4/mcg-rhel8-operator, ocs4/ocs-rhel8-operator, ocs4/rook-ceph-rhel8-operator
    affected: no fix planned “Out of support scope”
  • Red Hat Openshift Data Foundation 4 ocs4/mcg-rhel8-operator, odf4/odf-multicluster-rhel9-operator
    affected: no fix available, no fix planned “Will not fix”
  • Red Hat OpenShift GitOps openshift-gitops-1/argocd-rhel8, openshift-gitops-1/applicationset-rhel8
    affected: no fix available
show 6 more
  • Red Hat OpenShift Virtualization 4 container-native-virtualization/node-maintenance-operator, container-native-virtualization/kubernetes-nmstate-handler-rhel8
    affected: no fix available, no fix planned “Will not fix”
  • Red Hat Quay 3 quay/quay-operator-rhel8
    affected: no fix available
  • Red Hat OpenShift Container Platform 4.12 openshift-clients 4.12.0-202301042257.p0.g854f807.assembly.stream.el8, openshift-clients 4.12.0-202301042257.p0.g854f807.assembly.stream.el9, openshift4/ose-installer v4.12.0-202301271115.p0.g7fea1c4.assembly.stream, openshift4/metallb-rhel8-operator v4.12.0-202301301729.p0.g917cd33.assembly.stream, openshift-clients-redistributable 4.12.0-202301042257.p0.g854f807.assembly.stream.el8, openshift-clients-redistributable 4.12.0-202301042257.p0.g854f807.assembly.stream.el9, +1 more
    fixed: vendor fix RHSA-2022:7398
  • Red Hat OpenShift Container Platform 4.13 openshift4/ose-installer v4.13.0-202305091542.p0.g44db7b2.assembly.stream, openshift4/ose-machine-api-operator v4.13.0-202304190216.p0.ga23baf7.assembly.stream
    fixed: vendor fix RHSA-2023:1326
  • Red Hat RHODF 4.13 for RHEL 9 odf4/mcg-rhel9-operator v4.13.0-41, odf4/odf-rhel9-operator v4.13.0-24
    fixed: vendor fix RHSA-2023:3742
  • Red Hat Ironic content for Red Hat OpenShift Container Platform 4.12 tox 3.23.0-2.el9.1, crudini 0.9.3-4.el9, pysnmp 4.4.12-6.el9, future 0.18.2-9.el9.1, subunit 1.4.0-6.el9.1, pyflakes 2.2.0-3.el9.1, +451 more Red Hat Node Maintenance Operator workload-availability/node-maintenance-rhel8-operator Red Hat OpenShift Developer Tools and Services helm Red Hat OpenShift Service Mesh 2 openshift-service-mesh/istio-cni-rhel8 Red Hat Advanced Cluster Management for Kubernetes 2 rhacm2/multiclusterhub-repo-rhel8, rhacm2/multicluster-operators-channel-rhel8, rhacm2/multicluster-operators-subscription-rhel8 Red Hat OpenShift Container Platform 4 openshift, microshift, microshift-olm, microshift-sriov, microshift-multus, openshift-clients, +39 more
    +6 more products
    Red Hat OpenShift Container Platform 4.12 nmstate 1.3.3-1.el8, ostree 2022.2-5.el8, tini 0.16.1-1.el8ar, buildah 1.23.4-2.el8, grpc 1.18.0-4.el8ost, haproxy 2.2.24-1.el8, +466 more Red Hat OpenShift Container Platform 4.13 openshift4/ose-cli v4.13.0-202304190216.p0.g92b1a3d.assembly.stream, openshift4/ose-pod v4.13.0-202304211155.p0.gb404935.assembly.stream, openshift4/ose-etcd v4.13.0-202304190216.p0.gf70da9d.assembly.stream, openshift4/ose-tests v4.13.0-202305031828.p0.g893ae57.assembly.stream, openshift4/ose-console v4.13.0-202305031828.p0.ga551d28.assembly.stream, openshift4/ose-coredns v4.13.0-202304190216.p0.g5560e4a.assembly.stream, +173 more Red Hat Openshift Data Foundation 4 odf4/cephcsi-rhel9, odf4/ocs-rhel9-operator Red Hat OpenStack Platform 16.1 golang-gopkg-yaml-devel-v2 Red Hat OpenStack Platform 16.2 golang-gopkg-yaml-devel-v2 Red Hat RHODF 4.13 for RHEL 9 odf4/cephcsi-rhel9 v4.13.0-35, odf4/mcg-cli-rhel9 v4.13.0-17, odf4/mcg-core-rhel9 v4.13.0-41, odf4/odf-console-rhel9 v4.13.0-85, odf4/ocs-rhel9-operator v4.13.0-67, odf4/odr-rhel9-operator v4.13.0-33, +16 more
    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
Proof of concept is public
Automatable
no
Technical impact
partial
Assessed
18 mo ago

Exploit prediction

0.43% chance of exploitation in the next 30 days, higher than 37% of all scored CVEs (FIRST EPSS, 2026-11-08).

Exploits and checks

  • github.com https://github.com/go-yaml/yaml/pull/375 referenced PoC, tagged "exploit" by a source, unverified

CVSS scores

assigned by version score vector
CISA ADP 3.1 5.5 CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H
NVD 3.1 5.5 CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H
CNA 3.1 5.5 CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H
GitHub 3.1 5.5 CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H

Affected packages

ecosystem package affected fixed in
go gopkg.in/yaml.v2
<2.2.3
2.2.3
go github.com/go-yaml/yaml
<=2.1.0
all versions
 no fix listed

Affected products

  • gopkg.in/yaml.v2 gopkg.in/yaml.v2
  • github.com/go-yaml/yaml github.com/go-yaml/yaml

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.