{
    "id": "CVE-2021-29921",
    "published": "2021-05-06 13:15:12",
    "last_modified": "2026-06-17 03:48:27",
    "cvss_score": "9.8",
    "cvss_severity": "CRITICAL",
    "cvss_version": "3.1",
    "cvss_vector": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H",
    "cwe": null,
    "description": "In Python before 3,9,5, the ipaddress library mishandles leading zero characters in the octets of an IP address string. This (in some situations) allows attackers to bypass access control that is based on IP addresses.",
    "epss_score": "0.06882",
    "epss_percentile": "0.93878",
    "kev": 0,
    "kev_due": null,
    "has_exploit": 0,
    "updated_at": "2026-10-05 18:17:25",
    "priority": {
        "rank": 3,
        "label": "In your normal cycle",
        "why": "Critical by CVSS (9.8), but no sign of active exploitation."
    },
    "products": [
        {
            "vendor": "oracle",
            "product": "communications_cloud_native_core_automated_test_suite"
        },
        {
            "vendor": "oracle",
            "product": "communications_cloud_native_core_binding_support_function"
        },
        {
            "vendor": "oracle",
            "product": "communications_cloud_native_core_network_slice_selection_function"
        },
        {
            "vendor": "oracle",
            "product": "graalvm"
        },
        {
            "vendor": "oracle",
            "product": "zfs_storage_appliance_kit"
        },
        {
            "vendor": "python",
            "product": "python"
        }
    ],
    "kev_detail": null,
    "exploits": [],
    "refs_list": [
        "https://bugs.python.org/issue36384",
        "https://docs.python.org/3/library/ipaddress.html",
        "https://github.com/python/cpython/blob/63298930fb531ba2bb4f23bc3b915dbf1e17e9e1/Misc/NEWS.d/3.8.0a4.rst",
        "https://github.com/python/cpython/pull/12577",
        "https://github.com/python/cpython/pull/25099",
        "https://github.com/sickcodes",
        "https://github.com/sickcodes/security/blob/master/advisories/SICK-2021-014.md",
        "https://python-security.readthedocs.io/vuln/ipaddress-ipv4-leading-zeros.html",
        "https://security.gentoo.org/glsa/202305-02",
        "https://security.netapp.com/advisory/ntap-20210622-0003/",
        "https://sick.codes/sick-2021-014",
        "https://www.oracle.com//security-alerts/cpujul2021.html",
        "https://www.oracle.com/security-alerts/cpuapr2022.html",
        "https://www.oracle.com/security-alerts/cpujan2022.html",
        "https://www.oracle.com/security-alerts/cpujul2022.html",
        "https://www.oracle.com/security-alerts/cpuoct2021.html",
        "https://bugs.python.org/issue36384",
        "https://docs.python.org/3/library/ipaddress.html",
        "https://github.com/python/cpython/blob/63298930fb531ba2bb4f23bc3b915dbf1e17e9e1/Misc/NEWS.d/3.8.0a4.rst",
        "https://github.com/python/cpython/pull/12577",
        "https://github.com/python/cpython/pull/25099",
        "https://github.com/sickcodes",
        "https://github.com/sickcodes/security/blob/master/advisories/SICK-2021-014.md",
        "https://lists.debian.org/debian-lts-announce/2024/12/msg00000.html",
        "https://python-security.readthedocs.io/vuln/ipaddress-ipv4-leading-zeros.html"
    ]
}