CVE-2026-39821 Affecting golang-golang-x-net package, versions <1:0.55.0-1


Severity

Recommended
low

Based on default assessment until relevant scores are available.

Threat Intelligence

EPSS
0.69% (51st percentile)

Do your applications use this vulnerable package?

In a few clicks we can analyze your entire application and see what components are vulnerable in your application, and suggest you quick fixes.

Test your applications
  • Snyk IDSNYK-DEBIANUNSTABLE-GOLANGGOLANGXNET-17137524
  • published3 Jun 2026
  • disclosed22 May 2026

Introduced: 22 May 2026

CVE-2026-39821  (opens in a new tab)

How to fix?

Upgrade Debian:unstable golang-golang-x-net to version 1:0.55.0-1 or higher.

NVD Description

Note: Versions mentioned in the description apply only to the upstream golang-golang-x-net package and not the golang-golang-x-net package as distributed by Debian. See How to fix? for Debian:unstable 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