Addressable is an alternative implementation to the URI implementation that is part of Ruby's standard library. From 2.0.0 until 2.9.1, the pure-Ruby Addressable::IDNA.to_unicode implementation decodes invalid Punycode A-labels instead of returning them unchanged. Labels that decode to ASCII text or fail to convert back to the same A-label can therefore make Addressable::URI#display_uri show a trusted-looking host while host, normalized_host, and the connection target retain the attacker-controlled encoded host. A trusted-name comparison using Addressable::IDNA.to_unicode output can also treat two different hosts as the same without displaying the URI. The native libidn implementation, to_ascii, and normalized_host are unaffected. This issue is fixed in version 2.9.1.

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Advisories
Source ID Title
Github GHSA Github GHSA GHSA-9crm-g4mf-wc5j Addressable display_uri can show misleading hosts with invalid Punycode A-labels
Fixes

Solution

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Workaround

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History

Thu, 12 Nov 2026 22:15:00 +0000

Type Values Removed Values Added
Description Addressable is an alternative implementation to the URI implementation that is part of Ruby's standard library. From 2.0.0 until 2.9.1, the pure-Ruby Addressable::IDNA.to_unicode implementation decodes invalid Punycode A-labels instead of returning them unchanged. Labels that decode to ASCII text or fail to convert back to the same A-label can therefore make Addressable::URI#display_uri show a trusted-looking host while host, normalized_host, and the connection target retain the attacker-controlled encoded host. A trusted-name comparison using Addressable::IDNA.to_unicode output can also treat two different hosts as the same without displaying the URI. The native libidn implementation, to_ascii, and normalized_host are unaffected. This issue is fixed in version 2.9.1.
Title Addressable display_uri can show misleading hosts with invalid Punycode A-labels
Weaknesses CWE-1007
CWE-20
References
Metrics cvssV3_1

{'score': 4.3, 'vector': 'CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:L/A:N'}


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cve-icon MITRE

Status: PUBLISHED

Assigner: GitHub_M

Published:

Updated: 2026-11-13T00:34:23.442Z

Reserved: 2026-11-10T21:12:01.227Z

Link: CVE-2026-126348

cve-icon Vulnrichment

No data.

cve-icon NVD

Status : Received

Published: 2026-11-12T22:19:19.930

Modified: 2026-11-12T22:19:19.930

Link: CVE-2026-126348

cve-icon Redhat

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cve-icon OpenCVE Enrichment

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Weaknesses