idn2toascii_4i in lib/lookup.c in GNU libidn2 before 2.1.1 has a heap-based buffer overflow via a long domain string.
{
    "availability": "No subscription required",
    "binaries": [
        {
            "binary_name": "idn2",
            "binary_version": "2.0.4-1.1ubuntu0.2"
        },
        {
            "binary_name": "libidn2-0",
            "binary_version": "2.0.4-1.1ubuntu0.2"
        },
        {
            "binary_name": "libidn2-0-dev",
            "binary_version": "2.0.4-1.1ubuntu0.2"
        },
        {
            "binary_name": "libidn2-dev",
            "binary_version": "2.0.4-1.1ubuntu0.2"
        }
    ]
}