CVE-2026-52942 (GCVE-0-2026-52942)
Vulnerability from cvelistv5
Published
2026-06-24 07:14
Modified
2026-08-05 12:31
Severity ?
7.1 (High) - CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:H
Summary
In the Linux kernel, the following vulnerability has been resolved: netfilter: nf_log: validate MAC header was set before dumping it The fallback path of dump_mac_header() guards the MAC header access only with "skb->mac_header != skb->network_header", without checking skb_mac_header_was_set(). When the MAC header is unset, mac_header is 0xffff, so the test passes and skb_mac_header(skb) returns skb->head + 0xffff, ~64 KiB past the buffer; the loop then reads dev->hard_header_len bytes out of bounds into the kernel log. This is reachable via the netdev logger: nf_log_unknown_packet() calls dump_mac_header() unconditionally, and an skb sent through AF_PACKET with PACKET_QDISC_BYPASS reaches the egress hook with mac_header still unset (__dev_queue_xmit(), which would reset it, is bypassed). Add the skb_mac_header_was_set() check the ARPHRD_ETHER path already uses, and replace the open-coded MAC header length test with skb_mac_header_len(). Only skbs with an unset MAC header are affected; valid ones are dumped as before. BUG: KASAN: slab-out-of-bounds in dump_mac_header (net/netfilter/nf_log_syslog.c:831) Read of size 1 at addr ffff88800ea49d3f by task exploit/148 Call Trace: kasan_report (mm/kasan/report.c:595) dump_mac_header (net/netfilter/nf_log_syslog.c:831) nf_log_netdev_packet (net/netfilter/nf_log_syslog.c:938 net/netfilter/nf_log_syslog.c:963) nf_log_packet (net/netfilter/nf_log.c:260) nft_log_eval (net/netfilter/nft_log.c:60) nft_do_chain (net/netfilter/nf_tables_core.c:285) nft_do_chain_netdev (net/netfilter/nft_chain_filter.c:307) nf_hook_slow (net/netfilter/core.c:619) nf_hook_direct_egress (net/packet/af_packet.c:257) packet_xmit (net/packet/af_packet.c:280) packet_sendmsg (net/packet/af_packet.c:3114) __sys_sendto (net/socket.c:2265)
References
Impacted products
Vendor Product Version
Linux Linux Version: 7eb9282cd0efac08b8377cbd5037ba297c77e3f7
Version: 7eb9282cd0efac08b8377cbd5037ba297c77e3f7
Version: 7eb9282cd0efac08b8377cbd5037ba297c77e3f7
Version: 7eb9282cd0efac08b8377cbd5037ba297c77e3f7
Version: 7eb9282cd0efac08b8377cbd5037ba297c77e3f7
Version: 7eb9282cd0efac08b8377cbd5037ba297c77e3f7
Version: 7eb9282cd0efac08b8377cbd5037ba297c77e3f7
Version: 7eb9282cd0efac08b8377cbd5037ba297c77e3f7
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{
  "containers": {
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          "product": "Linux",
          "programFiles": [
            "net/netfilter/nf_log_syslog.c"
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          "vendor": "Linux",
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              "status": "unaffected",
              "version": "0",
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              "status": "unaffected",
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              "versionType": "original_commit_for_fix"
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        }
      ],
      "cpeApplicability": [
        {
          "nodes": [
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              "negate": false,
              "operator": "OR"
            }
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      ],
      "descriptions": [
        {
          "lang": "en",
          "value": "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-\u003emac_header != skb-\u003enetwork_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-\u003ehead + 0xffff, ~64 KiB past the buffer; the loop then reads\ndev-\u003ehard_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)"
        }
      ],
      "metrics": [
        {
          "cvssV3_1": {
            "baseScore": 7.1,
            "baseSeverity": "HIGH",
            "vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:H",
            "version": "3.1"
          },
          "scenarios": [
            {
              "lang": "en",
              "value": "AV:L - The vulnerable path is reached by local kernel interfaces: installing a netdev nftables log rule through nfnetlink and sending an AF_PACKET frame with PACKET_QDISC_BYPASS. It is not triggered directly by unauthenticated remote network packets.\nAC:L - There is no race or fragile timing requirement; once the rule, egress hook, and packet socket option are set, sending a crafted AF_PACKET frame reliably reaches dump_mac_header() with an unset MAC header. The attacker controls the triggering packet path.\nPR:L - The setup requires CAP_NET_ADMIN for nftables and CAP_NET_RAW for AF_PACKET, both namespace-relative and reachable by an unprivileged local user in user/network namespaces in a reasonable deployment where nf_log_all_netns permits netns logging. If only init_net logging is allowed, this rises to init-namespace admin, but the higher-severity reasonable user-namespace scenario is PR:L.\nUI:N - No victim action is required after the attacker has the needed local privileges. The attacker installs the rule and sends the packet themselves.\nS:U - The vulnerability affects kernel networking/logging resources within the same host security authority. It does not cross a VM, IOMMU, or other separate security boundary.\nC:H - The bug reads bytes from roughly 64 KiB past skb-\u003ehead and prints them into the kernel log, creating a repeatable kernel memory disclosure primitive. Although each log entry is bounded by dev-\u003ehard_header_len, repeated triggering and heap influence make high confidentiality impact defensible.\nI:N - The vulnerable operation is an out-of-bounds read used for logging MAC bytes. There is no write, object corruption, or control-flow modification primitive shown by the fix or reachable path.\nA:H - The reported reproducer triggers a KASAN slab-out-of-bounds BUG/oops in dump_mac_header(), and hardened/debug deployments may panic on this condition. The trigger can also be repeated locally, so high availability impact is defensible."
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-08-05T12:31:54.446Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
      },
      "references": [
        {
          "url": "https://git.kernel.org/stable/c/2e96e1bc9b4d5450e6c33f078e19a9bc1dda6c0b"
        },
        {
          "url": "https://git.kernel.org/stable/c/d704ee9c7bc68a161684c51a7ac05b446dcf38d4"
        },
        {
          "url": "https://git.kernel.org/stable/c/befb8968a2abdfa948d5600ea7f7a509a292a590"
        },
        {
          "url": "https://git.kernel.org/stable/c/8a81e336da685423f5b64aac4d571e63d674c52a"
        },
        {
          "url": "https://git.kernel.org/stable/c/c38d41134085193efd5b237cf513ad5b3421a60d"
        },
        {
          "url": "https://git.kernel.org/stable/c/af1b7699466f6556b351fa25d3dc870abfb5d310"
        },
        {
          "url": "https://git.kernel.org/stable/c/65ef7397eb9a296e91839f5fd10be96f23d332e7"
        },
        {
          "url": "https://git.kernel.org/stable/c/a84b6fedbc97078788be78dbdd7517d143ad1a77"
        }
      ],
      "title": "netfilter: nf_log: validate MAC header was set before dumping it",
      "x_generator": {
        "engine": "bippy-1.2.0"
      }
    }
  },
  "cveMetadata": {
    "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
    "assignerShortName": "Linux",
    "cveId": "CVE-2026-52942",
    "datePublished": "2026-06-24T07:14:30.610Z",
    "dateReserved": "2026-06-09T07:44:35.370Z",
    "dateUpdated": "2026-08-05T12:31:54.446Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2"
}


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