CVE-2019-12290: GNU LIBIDN2

High severity, CVSS 7.5. EPSS: 3.1% chance of exploitation in the next 30 days.

GNU libidn2 before 2.2.0 fails to perform the roundtrip checks specified in RFC3490 Section 4.2 when converting A-labels to U-labels. This makes it possible in some circumstances for one domain to impersonate another. By creating a malicious domain that matches a target domain except for the inclusion of certain punycoded Unicode characters (that would be discarded when converted first to a Unicode label and then back to an ASCII label), arbitrary domains can be impersonated.

Affected products

• GNU LIBIDN2: before 2.2.0 (fixed in 2.2.0)

Published 2019-10-22. Last modified 2026-06-17.