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CVE-2026-39821 affects the ToASCII and ToUnicode functions in golang.org/x/net/idna. The functions incorrectly accept Punycode-encoded labels whose decoded representation consists exclusively of ASCII characters, rather than rejecting those labels. This creates inconsistent hostname representations: an application can validate or authorize the encoded ASCII form, then convert it to Unicode and operate on an equivalent trusted ASCII hostname. The resulting validation bypass can lead to privilege escalation where hostname values are used as security principals, authorization boundaries, or access-control selectors.
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A privilege-escalation vulnerability in Go's golang.org/x/net/idna processing arising from incorrect Punycode label handling. It affects the dependency included in the patched RHEL 9 osbuild-composer packages.
A validation-bypass and potential privilege-escalation vulnerability in golang.org/x/net/idna involving ASCII-only Punycode-encoded labels.
A Go x/net/idna validation flaw in which ASCII-only Punycode-encoded labels are not rejected, enabling validation bypass and potential privilege escalation.
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Cross-references every affected SKU, including bundled OEM variants.
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