CVE-2026-39821

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Source
https://cve.org/CVERecord?id=CVE-2026-39821
Import Source
https://storage.googleapis.com/osv-test-cve-osv-conversion/osv-output/CVE-2026-39821.json
JSON Data
https://api.test.osv.dev/v1/vulns/CVE-2026-39821
Aliases
Downstream
Related
Published
2026-05-22T15:01:21.462Z
Modified
2026-06-09T18:29:40.899149745Z
Severity
  • 9.6 (Critical) CVSS_V3 - CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:N CVSS Calculator
Summary
Invoking failure to reject ASCII-only Punycode-encoded labels in golang.org/x/net/idna
Details

The ToASCII and ToUnicode functions incorrectly accept Punycode-encoded labels that decode to an ASCII-only label. For example, ToUnicode("xn--example-.com") incorrectly returns the name "example.com" rather than an error. This behavior can lead to privilege escalation in programs using the idna package. For example, a program which performs privilege checks on the ASCII hostname may reject "example.com" but permit "xn--example-.com". If that program subsequently converts the ASCII hostname to Unicode, it will inadvertently permits access to the Unicode name "example.com".

Database specific 
{
    "osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/39xxx/CVE-2026-39821.json",
    "unresolved_ranges": [
        {
            "source": "AFFECTED_FIELD",
            "extracted_events": [
                {
                    "fixed": "0.55.0"
                }
            ]
        }
    ],
    "cna_assigner": "Go"
}
References

Affected packages

Git / github.com/golang/net

Affected ranges

Type
GIT
Repo
https://github.com/golang/net
Events
Introduced
0 Unknown introduced commit / All previous commits are affected
Fixed
7770ec48d03fec35e378665337b4faca93c38423
Database specific 
{
    "source": "CPE_RANGE",
    "cpe": "cpe:2.3:a:golang:net:*:*:*:*:*:go:*:*",
    "extracted_events": [
        {
            "introduced": "0"
        },
        {
            "fixed": "0.55.0"
        }
    ]
}

Affected versions

v0.*
v0.1.0
v0.10.0
v0.11.0
v0.12.0
v0.13.0
v0.14.0
v0.15.0
v0.16.0
v0.17.0
v0.18.0
v0.19.0
v0.2.0
v0.20.0
v0.21.0
v0.22.0
v0.23.0
v0.24.0
v0.25.0
v0.26.0
v0.27.0
v0.28.0
v0.29.0
v0.3.0
v0.30.0
v0.31.0
v0.32.0
v0.33.0
v0.34.0
v0.35.0
v0.36.0
v0.37.0
v0.38.0
v0.39.0
v0.4.0
v0.40.0
v0.41.0
v0.42.0
v0.43.0
v0.44.0
v0.45.0
v0.46.0
v0.47.0
v0.48.0
v0.49.0
v0.5.0
v0.50.0
v0.51.0
v0.52.0
v0.53.0
v0.54.0
v0.6.0
v0.7.0
v0.8.0
v0.9.0

Database specific

source 
"https://storage.googleapis.com/osv-test-cve-osv-conversion/osv-output/CVE-2026-39821.json"