Improper Authentication Affecting golang.org/x/net/idna package, versions <0.54.0
Threat Intelligence
The probability is the direct output of the EPSS model, and conveys an overall sense of the threat of exploitation in the wild. The percentile measures the EPSS probability relative to all known EPSS scores. Note: This data is updated daily, relying on the latest available EPSS model version. Check out the EPSS documentation for more details.
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Start learning- Snyk IDSNYK-GOLANG-GOLANGORGXNETIDNA-17116876
- published1 Jun 2026
- disclosed22 May 2026
- creditKC1zs4
Introduced: 22 May 2026
CVE-2026-39821 Â (opens in a new tab)How to fix?
Upgrade golang.org/x/net/idna to version 0.54.0 or higher.
Overview
Affected versions of this package are vulnerable to Improper Authentication via the ToASCII and ToUnicode functions. An attacker can bypass hostname validation by submitting Punycode-encoded labels that decode to ASCII-only labels, potentially leading to privilege escalation in applications that rely on these functions for security checks.
Note: The fix depends on the Go toolchain in use having Unicode version 16 or later, which is planned for the 1.27 release.