CVE-2026-39821 Affecting golang package, versions <0:1.26.5-1.el10_2


Severity

Recommended
high

Based on Rocky Linux security rating.

Threat Intelligence

EPSS
0.66% (48th percentile)

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  • Snyk IDSNYK-ROCKY10-GOLANG-17961265
  • published14 Jul 2026
  • disclosed22 May 2026

Introduced: 22 May 2026

CVE-2026-39821  (opens in a new tab)

How to fix?

Upgrade Rocky-Linux:10 golang to version 0:1.26.5-1.el10_2 or higher.
This issue was patched in RLSA-2026:37436.

NVD Description

Note: Versions mentioned in the description apply only to the upstream golang package and not the golang package as distributed by Rocky-Linux. See How to fix? for Rocky-Linux:10 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