# CVE-2019-12290: idn2: GNU libidn2 before 2.2.0 fails to perform the roundtrip checks specified in RFC3490 Section 4.2 when converting A-lab...

CVE-2019-12290 is fixed in 2 products on 1 platform, first by idn2 2.0.4-1.1ubuntu0.2, released October 22, 2019. It is not reported as exploited. Patch Radar priority: Routine.

- Web page: https://patchblox.com/security/cve/CVE-2019-12290
- Priority: Routine
- CVSS: n/a (Medium)
- EPSS: 0.0323
- CISA KEV: not listed
- Exploited (vendor report): no
- Publicly disclosed: no
- Published: Oct 22, 2019

## Description

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.

## Where it's fixed

| Platform | Product | Fixed in | Fix | Released |
|---|---|---|---|---|
| Linux | idn2 Ubuntu 18.04.6 LTS (bionic) | 2.0.4-1.1ubuntu0.2 | [idn2 2.0.4-1.1ubuntu0.2](https://patchblox.com/security/data/fix/linux/ubuntu-bionic-idn2-2.0.4-1.1ubuntu0.2.md) | Oct 22, 2019 |
| Linux | libidn2-0 Ubuntu 18.04.6 LTS (bionic) | 2.0.4-1.1ubuntu0.2 | [libidn2-0 2.0.4-1.1ubuntu0.2](https://patchblox.com/security/data/fix/linux/ubuntu-bionic-libidn2-0-2.0.4-1.1ubuntu0.2.md) | Oct 22, 2019 |

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