DEBIAN-CVE-2026-39821

Advisory lineage Upstream: 1 Downstream: 0
Upstream
CVE-2026-39821
Published: 22 May 2026, 16:16
Last modified:15 Jun 2026, 19:06

Vulnerability Summary

Overall Risk (default)
high
70/100
CVSS Score
9.6 CRITICAL
3.1 (osv_debian)
EPSS Score
No data
KEV
Not listed
Ransomware
No reports
Public exploits
None found
Dark Web
Not detected

Timeline

22 May 2026, 16:16
Published
Vulnerability first disclosed
15 Jun 2026, 19:06
Last Modified
Vulnerability information updated

Description

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".

CVSS Metrics

  • v3.1•CRITICAL•Score: 9.6CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:N

Affected Systems

  • debian•golang-golang-x-net

    all | all | all | all | < 1:0.55.0-1

References (1)