netfilter: nft_ct: bail out on template ct in get eval_CVE-2026-53267

{
    "lastseen": "",
    "description": "In the Linux kernel, the following vulnerability has been resolved:\n\nnetfilter: nft_ct: bail out on template ct in get eval\n\nI noticed this issue while looking at a historic syzbot report [1].\n\nA rule like the one below is enough to trigger the bug:\n\n    table ip t {\n        chain pre {\n            type filter hook prerouting priority raw;\n            ct zone set 1\n            ct original saddr 1.2.3.4 accept\n        }\n    }\n\nThe first expression attaches a per-cpu template ct via\nnft_ct_set_zone_eval() (nf_ct_tmpl_alloc -> kzalloc, tuple is all\nzero, nf_ct_l3num(ct) == 0). The next expression then calls\nnft_ct_get_eval() on the same skb, treats the template as a real ct\nand hits the 16-byte memcpy path. With dreg at NFT_REG32_15 this\noverflows past struct nft_regs on the kernel stack; with smaller\ndreg values it silently clobbers adjacent registers.\n\nReject template ct at the eval entry and in nft_ct_get_fast_eval(),\nmirroring the check nft_ct_set_eval() already has. Additionally,\nbound the address copy in NFT_CT_SRC / NFT_CT_DST by priv->len\ninstead of by nf_ct_l3num(ct): nf_ct_get_tuple() zeroes the tuple\nbefore pkt_to_tuple() fills in only the protocol-relevant leading\nbytes, so the trailing bytes of tuple->{src,dst}.u3.all are\nwell-defined zero. priv->len is validated at rule load, so the\ncopy size is now bounded by the destination register rather than\nby an untrusted field on the conntrack.\n\n[1]: https://syzkaller.appspot.com/bug?id=389cf09cb72926114fce90dc85a2c3231dcb647c",
    "published": "2026-06-25T08:39:53.852Z",
    "modified": "2026-06-28T06:41:11.085Z",
    "type": "cve",
    "title": "netfilter: nft_ct: bail out on template ct in get eval",
    "source": "Linux",
    "references": "https://git.kernel.org/stable/c/af80f78ce984649e1698b841cd33f4fa505ad828\nhttps://git.kernel.org/stable/c/8470f676eadeab99132708acb1a85915664d6115\nhttps://git.kernel.org/stable/c/f071b0bf078146368d18e4eec386bf2ddc0ab7e0\nhttps://git.kernel.org/stable/c/2e154b5f53f1b0b490c7b8b02499f90feb86b1d5\nhttps://git.kernel.org/stable/c/3027ecbdb5fdf9200251c21d4818e4c447ef78e1",
    "id": "CVE-2026-53267",
    "bulletinFamily": "",
    "cwe": null,
    "cvelist": null,
    "sourceData": "Linux Linux 45d9bcda21f4c13be75e3571b0f0ef39e77934b5\nLinux Linux 45d9bcda21f4c13be75e3571b0f0ef39e77934b5\nLinux Linux 45d9bcda21f4c13be75e3571b0f0ef39e77934b5\nLinux Linux 45d9bcda21f4c13be75e3571b0f0ef39e77934b5\nLinux Linux 45d9bcda21f4c13be75e3571b0f0ef39e77934b5\nLinux Linux 4.1",
    "sourceHref": "",
    "cvss": {
        "score": 7.8,
        "severity": "HIGH",
        "vector": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H",
        "version": "3.1"
    },
    "cvss2": [],
    "cvss3": {
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        "vectorString": "",
        "baseScore": 0,
        "baseSeverity": "",
        "attackVector": "",
        "attackComplexity": "",
        "privilegesRequired": "",
        "userInteraction": "",
        "scope": "",
        "confidentialityImpact": "",
        "integrityImpact": "",
        "availabilityImpact": "",
        "cvssV3": {
            "version": "",
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            "baseScore": 0,
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            "privilegesRequired": "",
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    },
    "href": "",
    "category_name": "CVE",
    "post_link": "",
    "product": "Linux",
    "version": "45d9bcda21f4c13be75e3571b0f0ef39e77934b5",
    "vendor": "Linux",
    "ai_description": "",
    "ai_severity": "",
    "ai_vendor": "",
    "ai_product": "",
    "ai_version": "",
    "ai_score": 0
}