CRITICAL 10.0 Microsoft

CVE-2026-39821

Invoking failure to reject ASCII-only Punycode-encoded labels in golang.org/x/net/idna

Microsoft Security Update 2026-May: Invoking failure to reject ASCII-only Punycode-encoded labels in golang.org/x/net/idna

Affected Products

azl3 application-gateway-kubernetes-ingress 1.7.7-3 on Azure Linux 3.0
azl3 azcopy 10.25.1-4 on Azure Linux 3.0
azl3 azurelinux-image-tools 1.2.0-2 on Azure Linux 3.0
azl3 cert-manager 1.12.15-6 on Azure Linux 3.0
azl3 cf-cli 8.7.11-5 on Azure Linux 3.0
azl3 cloud-provider-kubevirt 0.5.1-3 on Azure Linux 3.0
azl3 containerd2 2.1.6-2 on Azure Linux 3.0
azl3 containerized-data-importer 1.62.0-3 on Azure Linux 3.0

References

Published: 2026-05-12 · Source: Microsoft · Feed updated: 2026-09-18

This critical severity vulnerability with a CVSS score of 10.0 was published on 2026-05-12 via Microsoft. Affected: azl3 application-gateway-kubernetes-ingress 1.7.7-3 on Azure Linux 3.0, azl3 azcopy 10.25.1-4 on Azure Linux 3.0, azl3 azurelinux-image-tools 1.2.0-2 on Azure Linux 3.0 and 5 more.

Risk Timeline

CVE Disclosed2026-05-12 · 128 days ago

Remediation Resources

Official Advisory

msrc.microsoft.com/update-guide/vulnerability/CVE-2026-39821

NVD / MITRE

nvd.nist.gov/vuln/detail/CVE-2026-39821

Related Vulnerabilities

CVE	Title	Severity	CVSS
CVE-2026-42960	Possible cache poisoning via promiscuous records for the authority section	CRITICAL	10.0
CVE-2026-46595	Invoking VerifiedPublicKeyCallback permissions skip enforcement in golang.org/x	CRITICAL	10.0
CVE-2025-68121	Unexpected session resumption in crypto/tls	CRITICAL	10.0
CVE-2026-27211	Cloud Hypervisor: Host File Exfiltration via QCOW Backing File Abuse	CRITICAL	10.0
CVE-2026-7374	Kubevirt: kubevirt virt-handler: privilege escalation and node compromise via sy	CRITICAL	9.9
CVE-2026-44210	Kata Containers have VM Escape via virtiofsd Argument Injection through Default-	CRITICAL	9.9

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