CVE intelligence

CVE-2026-126348

Vulnerability intelligence

Published Nov 12, 2026Sources checked Nov 13, 2026

4.3MEDIUMCVSS out of 10

What this means

Review the available evidence

CVE-2026-126348 and is rated Medium severity with a CVSS score of 4.3. It is not in the current CISA KEV record we collected. That does not prove exploitation has not occurred.

What to do next

Remediation and response

Microsoft Security Response Center guidance

Vendor revision: Nov 13, 2026

Release Notes

CISA KEVNot listedBased on the latest collected catalog

EPSSUnavailableNo current score collected

Ransomware useNot markedCISA KEV ransomware field

Threat actors0Source-linked actor relationships

Overview

What is CVE-2026-126348?

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.

Source: NVD