netfilter: nf_log: validate MAC header was set before dumping it_CVE-2026-52942

{
    "lastseen": "",
    "description": "In the Linux kernel, the following vulnerability has been resolved:\n\nnetfilter: nf_log: validate MAC header was set before dumping it\n\nThe fallback path of dump_mac_header() guards the MAC header access\nonly with \"skb->mac_header != skb->network_header\", without checking\nskb_mac_header_was_set(). When the MAC header is unset, mac_header is\n0xffff, so the test passes and skb_mac_header(skb) returns\nskb->head + 0xffff, ~64 KiB past the buffer; the loop then reads\ndev->hard_header_len bytes out of bounds into the kernel log.\n\nThis is reachable via the netdev logger: nf_log_unknown_packet() calls\ndump_mac_header() unconditionally, and an skb sent through AF_PACKET\nwith PACKET_QDISC_BYPASS reaches the egress hook with mac_header still\nunset (__dev_queue_xmit(), which would reset it, is bypassed).\n\nAdd the skb_mac_header_was_set() check the ARPHRD_ETHER path already\nuses, and replace the open-coded MAC header length test with\nskb_mac_header_len(). Only skbs with an unset MAC header are affected;\nvalid ones are dumped as before.\n\n BUG: KASAN: slab-out-of-bounds in dump_mac_header (net/netfilter/nf_log_syslog.c:831)\n Read of size 1 at addr ffff88800ea49d3f by task exploit/148\n Call Trace:\n  kasan_report (mm/kasan/report.c:595)\n  dump_mac_header (net/netfilter/nf_log_syslog.c:831)\n  nf_log_netdev_packet (net/netfilter/nf_log_syslog.c:938 net/netfilter/nf_log_syslog.c:963)\n  nf_log_packet (net/netfilter/nf_log.c:260)\n  nft_log_eval (net/netfilter/nft_log.c:60)\n  nft_do_chain (net/netfilter/nf_tables_core.c:285)\n  nft_do_chain_netdev (net/netfilter/nft_chain_filter.c:307)\n  nf_hook_slow (net/netfilter/core.c:619)\n  nf_hook_direct_egress (net/packet/af_packet.c:257)\n  packet_xmit (net/packet/af_packet.c:280)\n  packet_sendmsg (net/packet/af_packet.c:3114)\n  __sys_sendto (net/socket.c:2265)",
    "published": "2026-06-24T07:14:30.610Z",
    "modified": "2026-06-28T06:37:00.168Z",
    "type": "cve",
    "title": "netfilter: nf_log: validate MAC header was set before dumping it",
    "source": "Linux",
    "references": "https://git.kernel.org/stable/c/d704ee9c7bc68a161684c51a7ac05b446dcf38d4\nhttps://git.kernel.org/stable/c/befb8968a2abdfa948d5600ea7f7a509a292a590\nhttps://git.kernel.org/stable/c/8a81e336da685423f5b64aac4d571e63d674c52a\nhttps://git.kernel.org/stable/c/c38d41134085193efd5b237cf513ad5b3421a60d\nhttps://git.kernel.org/stable/c/af1b7699466f6556b351fa25d3dc870abfb5d310\nhttps://git.kernel.org/stable/c/65ef7397eb9a296e91839f5fd10be96f23d332e7\nhttps://git.kernel.org/stable/c/a84b6fedbc97078788be78dbdd7517d143ad1a77",
    "id": "CVE-2026-52942",
    "bulletinFamily": "",
    "cwe": null,
    "cvelist": null,
    "sourceData": "Linux Linux 7eb9282cd0efac08b8377cbd5037ba297c77e3f7\nLinux Linux 7eb9282cd0efac08b8377cbd5037ba297c77e3f7\nLinux Linux 7eb9282cd0efac08b8377cbd5037ba297c77e3f7\nLinux Linux 7eb9282cd0efac08b8377cbd5037ba297c77e3f7\nLinux Linux 7eb9282cd0efac08b8377cbd5037ba297c77e3f7\nLinux Linux 7eb9282cd0efac08b8377cbd5037ba297c77e3f7\nLinux Linux 7eb9282cd0efac08b8377cbd5037ba297c77e3f7\nLinux Linux 2.6.36",
    "sourceHref": "",
    "cvss": {
        "score": 7.1,
        "severity": "HIGH",
        "vector": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:H",
        "version": "3.1"
    },
    "cvss2": [],
    "cvss3": {
        "version": "",
        "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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            "availabilityImpact": ""
        }
    },
    "href": "",
    "category_name": "CVE",
    "post_link": "",
    "product": "Linux",
    "version": "7eb9282cd0efac08b8377cbd5037ba297c77e3f7",
    "vendor": "Linux",
    "ai_description": "",
    "ai_severity": "",
    "ai_vendor": "",
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    "ai_score": 0
}