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Golang.org/x/net Golang.org/x/net/idna vulnerabilities

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Published CVEs affecting Golang.org/x/net Golang.org/x/net/idna: 1 record(s), with affected versions and fixes.

CVE-2026-39821 Critical · 9.6 CWE-1289 May 22, 2026
Invoking failure to reject ASCII-only Punycode-encoded labels in golang.org/x/net/idna
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".