CVEvulnerability

CVE-2026-39821

9.6 CRITICAL Published 2026-05-22 Modified 2026-09-17 Official page ↗
Status
Modified
Published
2026-05-22
Last modified
2026-09-17
Assigner
[email protected]
CVSS 3.1 (134c704f-9b21-4f2e-91b3-4a467353bcc0)
9.6 CRITICAL — CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:N
CVSS 3.1 (0b0ca135-0b70-47e7-9f44-1890c2a1c46c)
8.2 HIGH — CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:C/C:H/I:H/A:N
Weaknesses
CWE-1289

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".

Affected configurations

• golang net (< 0.55.0)

Related

Weakness · CWE (1)

  • CWE-1289 Improper Validation of Unsafe Equivalence in Input weakness

References