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Fencer Vulns
high 7.5

CVE-2026-27145 json

Inefficient candidate hostname parsing in crypto/x509

published 2026-06-02 5 mo ago modified 2026-10-02 38 d ago also BIT-golang-2026-27145 , EUVD-2026-34038 , GO-2026-5037

cvss
7.5
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
0.6%
EPSS 0.6% chance of exploitation in 30 days, percentile 48%
public exploits
0
none known

Summary

(*x509.Certificate).VerifyHostname previously called matchHostnames in a loop over all DNS Subject Alternative Name (SAN) entries. This caused strings.Split(host, ".") to execute repeatedly on the same input hostname. With a large DNS SAN list, verification costs scaled quadratically based on the number of SAN entries multiplied by the hostname's label count. Because x509.Verify validates hostnames before building the certificate chain, this overhead occurred even for untrusted certificates.

Patch / fix

  • bitnami golang 1.25.11, 1.26.4
  • go stdlib 1.25.11, 1.26.4
  • Go standard library crypto/x509 1.25.11, 1.26.4
  • Red Hat Red Hat Ansible Automation Platform 2.5 for RHEL 8 0:1.6.7-1.el8ap
  • Red Hat Red Hat Ansible Automation Platform 2.5 for RHEL 9 0:1.6.7-1.el9ap
  • Red Hat Red Hat Ansible Automation Platform 2.6 for RHEL 10 0:1.6.6-1.el10ap
  • Red Hat Red Hat Ansible Automation Platform 2.6 for RHEL 9 0:1.6.6-1.el9ap
  • Red Hat Red Hat Ansible Automation Platform 2.7 for RHEL 10 0:1.6.6-1.el10ap
  • Red Hat Red Hat Ansible Automation Platform 2.7 for RHEL 9 0:1.6.6-1.el9ap
  • Red Hat Red Hat Enterprise Linux 10 0:0.2.10-1.el10_2, 0:0.4.9.2-1.el10_2, 0:0.9.27-7.el10_2.2, 0:0.152.1-1.el10_2, 0:1.0.0-4.el10_2.5, 0:1.0.1-2.el10_2.3, 0:1.26.4-1.el10_2, 1:0.3.8-6.el10_2
  • Red Hat Red Hat Enterprise Linux 10.0 Extended Update Support 0:0.2.3-6.el10_0, 0:0.4.7-5.el10_0, 0:0.152.1-1.el10_0, 0:1.26.1-1.el10_0, 0:1.26.5-1.el10_0, 1:0.3.2-5.el10_0
  • Red Hat Red Hat Enterprise Linux 7 Extended Lifecycle Support 0:1.4.0-8.el7_9
  • Red Hat Red Hat Enterprise Linux 8 1:0.2.5-9.el8_10, 8100020260710105056.a3795dee
  • Red Hat Red Hat Enterprise Linux 9 0:0.152.1-1.el9_8, 0:1.26.4-1.el9_8, 1:0.2.7-8.el9_8, 2:1.22.2-7.el9_8
  • Red Hat Red Hat Enterprise Linux 9.2 Update Services for SAP Solutions 0:1.26.5-1.el9_2, 1:0.2.2-1.el9_2.4
  • Red Hat Red Hat Enterprise Linux 9.4 Update Services for SAP Solutions 0:0.152.1-1.el9_4, 0:1.26.5-1.el9_4, 1:0.2.4-9.el9_4
  • Red Hat Red Hat Enterprise Linux 9.6 Extended Update Support 0:0.152.1-1.el9_6, 0:1.26.5-1.el9_6, 1:0.2.7-1.el9_6.5
  • Red Hat Red Hat OpenShift Container Platform 4.18 0:0.23.0-5.rhaos4.18.el8, 1786754425
  • Red Hat Red Hat OpenStack Platform 16.2 0:0.2.1-1.1.el8ost
  • Red Hat Red Hat Satellite 6.16 for RHEL 8 0:0.0.4-1.el8sat
  • Red Hat Red Hat Satellite 6.16 for RHEL 9 0:0.0.4-1.el9sat
  • Red Hat Red Hat Satellite 6.17 for RHEL 9 0:0.0.4-1.el9sat
  • Red Hat Red Hat Satellite 6.18 for RHEL 9 0:0.0.4-1.el9sat
  • Red Hat Red Hat Satellite 6.19 for RHEL 9 0:0.0.4-1.el9sat
  • Red Hat RHEM 1.1 for RHEL 10 0:1.1.4-1.el10em
  • Red Hat RHEM 1.1 for RHEL 9 0:1.1.4-1.el9em
  • Red Hat RHEM 1.2 for RHEL 10 0:1.2.1-1.el10
  • Red Hat RHEM 1.2 for RHEL 9 0:1.2.1-1.el9
  • Red Hat Cert Manager support for Red Hat OpenShift release 1.19 1786613805
  • Red Hat Cluster Observability Operator 1.5.0 1787593946
  • golang-1.26 Debian 14 1.26.4-1

debian advisories DEBIAN-CVE-2026-27145

  • cri-o openshift 4.12 1.25.5-37.rhaos4.12.git2e7f657.el8
  • cri-o openshift 4.12 1.25.5-8.rhaos4.12.git6120b13.el9
  • cri-tools openshift 4.12 1.25.0-8.el8
  • cri-tools openshift 4.12 1.25.0-7.el9
  • openshift openshift 4.12 4.12.0-202609111749.p2.g0e18cfc.assembly.stream.el8
  • openshift openshift 4.12 4.12.0-202609111749.p2.g0e18cfc.assembly.stream.el9
  • openshift-clients openshift 4.12 4.12.0-202609111749.p2.gd691257.assembly.stream.el8
  • openshift-clients openshift 4.12 4.12.0-202609111749.p2.gd691257.assembly.stream.el9

red hat advisories RHSA-2026:70645RHSA-2026:68334RHSA-2026:68335RHSA-2026:61253RHSA-2026:60354RHSA-2026:60315

  • go1.25-openssl SLES for SAP 15 SP6, SLES 15 SP6-LTSS, SLE Module for Development Tools 15 SP7 1.25.12-150600.13.21.1
  • go1.26-openssl SLES for SAP 15 SP6, SLES 15 SP6-LTSS, SLE Module for Development Tools 15 SP7 1.26.5-150600.13.9.1
  • go1.26-openssl SLES for SAP 15 SP5, SLES for SAP 15 SP4, SLES 15 SP5-LTSS +5 more 1.26.5-150000.1.12.1
  • go1.25-openssl SLES for SAP 15 SP5, SLES for SAP 15 SP4, SLES 15 SP5-LTSS +5 more 1.25.12-150000.1.27.1
  • go1.25-openssl SLES for SAP applications 16.0, SLES 16.0 1.25.12-160000.1.1
  • go1.26-openssl SLES for SAP applications 16.0, SLES 16.0 1.26.4-160000.1.1
  • go1.25 SLES for SAP applications 16.0, SLES 16.0 1.25.11-160000.1.1
  • go1.26 SLES for SAP applications 16.0, SLES 16.0 1.26.4-160000.1.1

suse advisories SUSE-SU-2026:3151-1SUSE-SU-2026:3102-1SUSE-SU-2026:3047-1SUSE-SU-2026:3046-1SUSE-SU-2026:22638-1SUSE-SU-2026:22572-1

  • govulncheck-vulndb openSUSE Leap 16.0 0.0.20260723T184607-160000.1.1
  • rclone openSUSE Leap 16.0 1.74.4-bp160.1.1
  • go1.25-openssl openSUSE Leap 16.0 1.25.12-160000.1.1
  • go1.26-openssl openSUSE Leap 16.0 1.26.4-160000.1.1
  • go1.25 openSUSE Leap 16.0 1.25.11-160000.1.1
  • go1.26 openSUSE Leap 16.0 1.26.4-160000.1.1
  • rclone openSUSE Tumbleweed 1.74.3-1.1
  • go1.25 openSUSE Tumbleweed 1.25.11-1.1

opensuse advisories openSUSE-SU-2026:21483-1openSUSE-SU-2026:21436-1openSUSE-SU-2026:21319-1openSUSE-SU-2026:21254-1openSUSE-SU-2026:20977-1openSUSE-SU-2026:20976-1

  • go-fdo-client AlmaLinux 10 1.0.0-4.el10_2.5
  • go-fdo-server AlmaLinux 10 1.0.1-2.el10_2.3
  • go-fdo-server-owner AlmaLinux 10 1.0.1-2.el10_2.3
  • go-fdo-server-rendezvous AlmaLinux 10 1.0.1-2.el10_2.3
  • go-fdo-server-manufacturer AlmaLinux 10 1.0.1-2.el10_2.3
  • yggdrasil AlmaLinux 10 0.4.9.2-1.el10_2
  • delve AlmaLinux 8 1.26.1-1.module_el8.10.0+4223+bd807c2e
  • golang AlmaLinux 8 1.26.5-1.module_el8.10.0+4223+bd807c2e

almalinux advisories ALSA-2026:46394ALSA-2026:46395ALSA-2026:39573ALSA-2026:38995ALSA-2026:36317ALSA-2026:35832

  • go-fdo-client Rocky Linux 10 1.0.0-4.el10_2.5
  • go-fdo-server Rocky Linux 10 1.0.1-2.el10_2.3
  • yggdrasil Rocky Linux 10 0.4.9.2-1.el10_2
  • delve Rocky Linux 8 1.26.1-1.module+el8.10.0+40244+e7cb3ff8
  • golang Rocky Linux 8 1.26.5-1.module+el8.10.0+40244+e7cb3ff8
  • skopeo Rocky Linux 9 2:1.22.2-7.el9_8
  • opentelemetry-collector Rocky Linux 10 0.152.1-1.el10_2
  • golang-github-openprinting-ipp-usb Rocky Linux 10 0.9.27-7.el10_2.2

rocky linux advisories RLSA-2026:46394RLSA-2026:46395RLSA-2026:39573RLSA-2026:38995RLSA-2026:36317RLSA-2026:34357

  • golang Azure Linux 3.0 1.25.11-1
  • golang Azure Linux 3.0 1.26.4-1

azure linux advisories AZL-89381AZL-89384

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-2026-27145 updated cvss 7.5

crypto/x509: golang: golang crypto/x509: Denial of Service via excessive processing of DNS SAN entries

  • Red Hat Assisted Installer for Red Hat OpenShift Container Platform 2 rhai/assisted-installer-rhel9
    affected: workaround, no fix available
  • Red Hat Confidential Compute Attestation openshift-sandboxed-containers/osc-monitor-rhel9
    affected: workaround, no fix planned “Will not fix”
  • Red Hat Deployment Validation Operator dvo/deployment-validation-rhel8-operator Red Hat ExternalDNS Operator edo/external-dns-rhel9, edo/external-dns-rhel9-operator Red Hat Fence Agents Remediation Operator workload-availability/fence-agents-remediation-rhel8-operator Red Hat File Integrity Operator compliance/openshift-file-integrity-rhel8-operator
    affected: workaround, no fix available
  • Red Hat Logging Subsystem for Red Hat OpenShift openshift-logging/cluster-logging-rhel9-operator
    affected: workaround, no fix planned “Will not fix”
  • Red Hat Machine Deletion Remediation Operator workload-availability/machine-deletion-remediation-rhel8-operator Red Hat Multiarch Tuning Operator multiarch-tuning/multiarch-tuning-rhel9-operator Red Hat Multicluster Engine for Kubernetes multicluster-engine/hive-rhel9, multicluster-engine/maestro-rhel9, multicluster-engine/assisted-service-9-rhel9 Red Hat Multicluster Engine for Kubernetes 5 multicluster-engine/clusterclaims-controller-rhel9, multicluster-engine/cluster-curator-controller-rhel9, multicluster-engine/cluster-image-set-controller-rhel9, multicluster-engine/provider-credential-controller-rhel9 Red Hat Network Observability Operator network-observability/network-observability-cli-rhel9 Red Hat Node HealthCheck Operator workload-availability/node-healthcheck-rhel8-operator, node-healthcheck-operator-tech-preview/node-healthcheck-operator-rhel8, node-healthcheck-operator-tech-preview/node-healthcheck-rhel8-operator
    +8 more products
    Red Hat OpenShift Lightspeed openshift-lightspeed/lightspeed-rhel9-operator Red Hat OpenShift Pipelines openshift-pipelines-client, openshift-pipelines/pipelines-scheduler-rhel9 Red Hat OpenShift Serverless openshift-serverless-clients Red Hat OpenShift Service Mesh 3 rh-osbs/openshift-golang-builder Red Hat Power monitoring for Red Hat OpenShift openshift-power-monitoring/kepler-rhel9 Red Hat 3scale API Management Platform 2 3scale-amp2/3scale-rhel9-operator Red Hat Advanced Cluster Management for Kubernetes 2 rhacm2/klusterlet-addon-controller-rhel9, rhacm2/acm-volsync-addon-controller-rhel9 Red Hat Advanced Cluster Management for Kubernetes 5 rhacm2/multicloud-integrations-rhel9, rhacm2/multicluster-operators-channel-rhel9, rhacm2/multicluster-operators-application-rhel9, rhacm2/multicluster-operators-subscription-rhel9
    affected: workaround, no fix available
  • Red Hat Ceph Storage 5 rhceph/snmp-notifier-rhel8 Red Hat Ceph Storage 6 rhceph/snmp-notifier-rhel9
    affected: workaround, no fix available “Fix deferred”
  • Red Hat Connectivity Link 1 rhcl-1/coredns-rhel9, rhcl-1/authorino-rhel9 Red Hat Enterprise Linux 7 rhc Red Hat Enterprise Linux 9 gvisor-tap-vsock, containernetworking-plugins, gvisor-tap-vsock-gvforwarder Red Hat Enterprise Linux 10 delve, gvisor-tap-vsock Red Hat Enterprise Linux AI (RHEL AI) 3 golang Red Hat OpenShift AI (RHOAI) rhoai/rhai-cli-rhel9
    +2 more products
    Red Hat OpenShift Cluster Manager CLI ocm-cli-clients/ocm-cli-rhel9 Red Hat OpenShift Container Platform 4 openshift4/ose-cli-rhel9, openshift4/ose-ansible-operator, rh-osbs/openshift-golang-builder, openshift4/ose-kube-rbac-proxy-rhel9, openshift4/ose-vertical-pod-autoscaler-rhel9, openshift4/ose-vertical-pod-autoscaler-rhel9-operator
    affected: workaround, no fix available
  • Red Hat OpenShift Container Platform 5 cri-o, butane, cri-tools, openshift, openshift5/frr-rhel9, ose-crio-credential-provider, +5 more
    affected: workaround, no fix available, no fix planned “Will not fix”
show 2 more
  • Red Hat OpenShift Dev Workspaces Operator devworkspace/devworkspace-rhel9-operator Red Hat OpenShift on AWS rosa Red Hat OpenShift Virtualization 4 rh-osbs/openshift-golang-builder Red Hat OpenStack Platform 16.2 golang-github-infrawatch-apputils Red Hat OpenStack Platform 17.1 rhosp-rhel9/osp-director-agent, golang-github-infrawatch-apputils Red Hat Satellite 6 yggdrasil-worker-forwarder
    +1 more products
    Red Hat Trusted Artifact Signer rhtas/ec-rhel9
    affected: workaround, no fix available
  • Red Hat Zero Trust Workload Identity Manager zero-trust-workload-identity-manager/spiffe-csi-driver-rhel9
    affected: workaround, no fix planned “Will not fix”

1 more affected, 93 more fixed, 107 more not affected in the full advisory

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
partial
Assessed
5 mo ago

Exploit prediction

0.59% chance of exploitation in the next 30 days, higher than 48% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by version score vector
CISA ADP 3.1 6.5 CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:L/A:H
CISA ADP 3.1 7.5 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
CNA 3.1 6.5 CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:L/A:H
CNA 3.1 7.5 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
OSV 3.1 7.5 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Affected packages

ecosystem package affected fixed in
bitnami golang
<1.25.11
>=1.26.0-0, <1.26.4
1.25.11
1.26.4
go stdlib
<1.25.11
>=1.26.0-0, <1.26.4
1.25.11
1.26.4

Affected products

  • Go standard library crypto/x509
  • Red Hat Red Hat Ansible Automation Platform 2.5 for RHEL 8
  • Red Hat Red Hat Ansible Automation Platform 2.5 for RHEL 9
  • Red Hat Red Hat Ansible Automation Platform 2.6 for RHEL 10
  • Red Hat Red Hat Ansible Automation Platform 2.6 for RHEL 9
  • Red Hat Red Hat Ansible Automation Platform 2.7 for RHEL 10
  • Red Hat Red Hat Ansible Automation Platform 2.7 for RHEL 9
  • Red Hat Red Hat Enterprise Linux 10
  • Red Hat Red Hat Enterprise Linux 10.0 Extended Update Support
  • Red Hat Red Hat Enterprise Linux 7 Extended Lifecycle Support
  • Red Hat Red Hat Enterprise Linux 8
  • Red Hat Red Hat Enterprise Linux 9
  • Red Hat Red Hat Enterprise Linux 9.2 Update Services for SAP Solutions
  • Red Hat Red Hat Enterprise Linux 9.4 Update Services for SAP Solutions
  • Red Hat Red Hat Enterprise Linux 9.6 Extended Update Support
  • Red Hat Red Hat OpenShift Container Platform 4.18
  • Red Hat Red Hat OpenStack Platform 16.2
  • Red Hat Red Hat Satellite 6.16 for RHEL 8
  • Red Hat Red Hat Satellite 6.16 for RHEL 9
  • Red Hat Red Hat Satellite 6.17 for RHEL 9
  • Red Hat Red Hat Satellite 6.18 for RHEL 9
  • Red Hat Red Hat Satellite 6.19 for RHEL 9
  • Red Hat RHEM 1.1 for RHEL 10
  • Red Hat RHEM 1.1 for RHEL 9
  • Red Hat RHEM 1.2 for RHEL 10
  • Red Hat RHEM 1.2 for RHEL 9
  • Red Hat Streams for Apache Kafka 3.2.1
  • Red Hat Cert Manager support for Red Hat OpenShift release 1.19
  • Red Hat Cluster Observability Operator 1.5.0
  • Red Hat Compliance Operator 1
  • Red Hat external secrets operator for Red Hat OpenShift 1.1
  • Red Hat multicluster engine for Kubernetes 2.1
  • Red Hat multicluster engine for Kubernetes 2.11
  • Red Hat multicluster engine for Kubernetes 2.17
  • Red Hat multicluster engine for Kubernetes 2.6
  • Red Hat multicluster engine for Kubernetes 2.8
  • Red Hat multicluster engine for Kubernetes 2.9
  • Red Hat Multicluster Global Hub 1.4.5
  • Red Hat Multicluster Global Hub 1.6.5
  • Red Hat Multicluster Global Hub 1.7.0
  • Red Hat Multicluster Global Hub 1.8.0
  • Red Hat OpenShift API for Data Protection 1.5
  • Red Hat OpenShift Developer Tools and Services 1.6.3
  • Red Hat Red Hat Advanced Cluster Management for Kubernetes 2.11
  • Red Hat Red Hat Advanced Cluster Management for Kubernetes 2.13
  • Red Hat Red Hat Advanced Cluster Management for Kubernetes 2.14
  • Red Hat Red Hat Advanced Cluster Management for Kubernetes 2.15
  • Red Hat Red Hat Advanced Cluster Management for Kubernetes 2.16
  • Red Hat Red Hat Advanced Cluster Management for Kubernetes 2.17
  • Red Hat Red Hat Ansible Automation Platform 2.7

Classification

Weakness
  • CWE-606 Unchecked Input for Loop Condition

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.

CPEs and fixed versions use Anchore's correction of NVD's data: Added CPE configurations because not yet analyzed by NVD.