CVE-2019-12290

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.

CVSS 3.1

7.5CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N

EPSS

3.2% chance of exploitation in the next 30 days; higher than 88% of CVEs (scores of 2026-10-25)

CWE

CWE-20

Published

2019-10-22

Modified

2026-10-14

Record from

the NVD, synced 2026-10-19

Affected

• gnu:libidn2

References

• http://lists.opensuse.org/opensuse-security-announce/2019-12/msg00008.html
• http://lists.opensuse.org/opensuse-security-announce/2019-12/msg00009.html
• https://gitlab.com/libidn/libidn2/commit/241e8f486134793cb0f4a5b0e5817a97883401f5
• https://gitlab.com/libidn/libidn2/commit/614117ef6e4c60e1950d742e3edf0a0ef8d389de
• https://gitlab.com/libidn/libidn2/merge_requests/71

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