CVE-2026-39821 Affecting go package, versions <1.26.8-r0


Severity

Recommended
low

Based on default assessment until relevant scores are available.

Threat Intelligence

EPSS
0.69% (51st percentile)

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  • Snyk IDSNYK-ALPINE324-GO-19533390
  • published5 Sept 2026
  • disclosed22 May 2026

Introduced: 22 May 2026

CVE-2026-39821  (opens in a new tab)

How to fix?

Upgrade Alpine:3.24 go to version 1.26.8-r0 or higher.

NVD Description

Note: Versions mentioned in the description apply only to the upstream go package and not the go package as distributed by Alpine. See How to fix? for Alpine:3.24 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