CVE-2026-39821 Affecting osbuild-composer-worker package, versions <0:101.5-2.el8_10.alma.1


Severity

Recommended
high

Based on AlmaLinux security rating.

Threat Intelligence

EPSS
0.69% (51st percentile)

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  • Snyk IDSNYK-ALMALINUX8-OSBUILDCOMPOSERWORKER-19675796
  • published11 Sept 2026
  • disclosed14 Jul 2026

Introduced: 14 Jul 2026

CVE-2026-39821  (opens in a new tab)

How to fix?

Upgrade AlmaLinux:8 osbuild-composer-worker to version 0:101.5-2.el8_10.alma.1 or higher.
This issue was patched in ALSA-2026:66016.

NVD Description

Note: Versions mentioned in the description apply only to the upstream osbuild-composer-worker package and not the osbuild-composer-worker package as distributed by AlmaLinux. See How to fix? for AlmaLinux:8 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