CVE-2026-39821 Affecting golang-golang-x-net-dev package, versions <1:0.0+git20190811.74dc4d7+dfsg-1ubuntu0.1~esm3


Severity

Recommended
medium

Based on Ubuntu security rating.

Threat Intelligence

EPSS
0.66% (48th percentile)

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  • Snyk IDSNYK-UBUNTU2004-GOLANGGOLANGXNETDEV-16877258
  • published9 Jun 2026
  • disclosed22 May 2026

Introduced: 22 May 2026

CVE-2026-39821  (opens in a new tab)

How to fix?

Upgrade Ubuntu:20.04 golang-golang-x-net-dev to version 1:0.0+git20190811.74dc4d7+dfsg-1ubuntu0.1~esm3 or higher.

NVD Description

Note: Versions mentioned in the description apply only to the upstream golang-golang-x-net-dev package and not the golang-golang-x-net-dev package as distributed by Ubuntu. See How to fix? for Ubuntu:20.04 relevant fixed versions and status.

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".

References

CVSS Base Scores

version 3.1