GO-2026-5026
Invoking failure to reject ASCII-only Punycode-encoded labels in golang.org/x/net/idna
At a glance
- Published
- Updated
- CVE
- CVE-2026-39821
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 packages
| Package | Versions |
|---|---|
| Go · stdlib | introduced 0, fixed 1.25.13, introduced 1.26.0-0, fixed 1.26.6, introduced 1.27.0-0, fixed 1.27.0-rc.3 |
| Go · golang.org/x/net | introduced 0, fixed 0.55.0 |
References
- https://go.dev/cl/767220 FIX
- https://go.dev/issue/78760 REPORT
- https://groups.google.com/g/golang-announce/c/iI-mYSI0lu8 WEB
- https://groups.google.com/g/golang-announce/c/94pEornpRlI WEB
Sources
| Source | Licence |
|---|---|
| OSV.dev | CC-BY 4.0 — Go Vulnerability Database |