CVE-2026-52942 (GCVE-0-2026-52942)

Vulnerability from cvelistv5 – Published: 2026-06-24 07:14 – Updated: 2026-09-08 08:49
VLAI
Title
netfilter: nf_log: validate MAC header was set before dumping it
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)
Severity
7.1 (High)
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:H
Assigner
References
Impacted products
Vendor Product Version CPE status
Linux Linux Affected: 7eb9282cd0efac08b8377cbd5037ba297c77e3f7 , < 2e96e1bc9b4d5450e6c33f078e19a9bc1dda6c0b (git)
Affected: 7eb9282cd0efac08b8377cbd5037ba297c77e3f7 , < d704ee9c7bc68a161684c51a7ac05b446dcf38d4 (git)
Affected: 7eb9282cd0efac08b8377cbd5037ba297c77e3f7 , < befb8968a2abdfa948d5600ea7f7a509a292a590 (git)
Affected: 7eb9282cd0efac08b8377cbd5037ba297c77e3f7 , < 8a81e336da685423f5b64aac4d571e63d674c52a (git)
Affected: 7eb9282cd0efac08b8377cbd5037ba297c77e3f7 , < c38d41134085193efd5b237cf513ad5b3421a60d (git)
Affected: 7eb9282cd0efac08b8377cbd5037ba297c77e3f7 , < af1b7699466f6556b351fa25d3dc870abfb5d310 (git)
Affected: 7eb9282cd0efac08b8377cbd5037ba297c77e3f7 , < 65ef7397eb9a296e91839f5fd10be96f23d332e7 (git)
Affected: 7eb9282cd0efac08b8377cbd5037ba297c77e3f7 , < a84b6fedbc97078788be78dbdd7517d143ad1a77 (git)
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Linux Linux Affected: 2.6.36
Unaffected: 0 , < 2.6.36 (semver)
Unaffected: 5.10.261 , ≤ 5.10.* (semver)
Unaffected: 5.15.210 , ≤ 5.15.* (semver)
Unaffected: 6.1.176 , ≤ 6.1.* (semver)
Unaffected: 6.6.143 , ≤ 6.6.* (semver)
Unaffected: 6.12.94 , ≤ 6.12.* (semver)
Unaffected: 6.18.36 , ≤ 6.18.* (semver)
Unaffected: 7.0.13 , ≤ 7.0.* (semver)
Unaffected: 7.1 , ≤ * (original_commit_for_fix)
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Siemens SIMATIC S7-1500 CPU 1518-4 PN/DP MFP Affected: V3.1.6 , < * (custom)
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Siemens SIMATIC S7-1500 CPU 1518F-4 PN/DP MFP Affected: V3.1.6 , < * (custom)
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Siemens SIPLUS S7-1500 CPU 1518-4 PN/DP MFP Affected: V3.1.6 , < * (custom)
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              "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."
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                "vendor": "Siemens",
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                    "version": "V3.1.6",
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                "vendor": "Siemens",
                "versions": [
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                "vendor": "Siemens",
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                    "status": "affected",
                    "version": "V3.1.6",
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            "source": "0b142b55-0307-4c5a-b3c9-f314f3fb7c5e"
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        "cveTags": [],
        "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)"
          }
        ],
        "id": "CVE-2026-52942",
        "lastModified": "2026-09-08T09:18:11.710",
        "metrics": {
          "cvssMetricV31": [
            {
              "cvssData": {
                "attackComplexity": "LOW",
                "attackVector": "LOCAL",
                "availabilityImpact": "HIGH",
                "baseScore": 7.1,
                "baseSeverity": "HIGH",
                "confidentialityImpact": "HIGH",
                "integrityImpact": "NONE",
                "privilegesRequired": "LOW",
                "scope": "UNCHANGED",
                "userInteraction": "NONE",
                "vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:H",
                "version": "3.1"
              },
              "exploitabilityScore": 1.8,
              "impactScore": 5.2,
              "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
              "type": "Secondary"
            }
          ]
        },
        "published": "2026-06-24T08:16:24.490",
        "references": [
          {
            "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
            "url": "https://git.kernel.org/stable/c/2e96e1bc9b4d5450e6c33f078e19a9bc1dda6c0b"
          },
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            "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
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            "source": "0b142b55-0307-4c5a-b3c9-f314f3fb7c5e",
            "url": "https://cert-portal.siemens.com/productcert/html/ssa-019113.html"
          }
        ],
        "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "vulnStatus": "Modified",
        "weaknesses": [
          {
            "description": [
              {
                "lang": "en",
                "value": "CWE-125"
              }
            ],
            "source": "nvd@nist.gov",
            "type": "Primary"
          }
        ]
      }
    },
    "redhat_vex": {
      "aggregate_severity": "Moderate",
      "current_release_date": "2026-09-10T06:32:15+00:00",
      "cve": "CVE-2026-52942",
      "id": "CVE-2026-52942",
      "initial_release_date": "2026-06-24T00:00:00+00:00",
      "product_status:fixed": "150",
      "product_status:known_affected": "184",
      "product_status:known_not_affected": "42",
      "source": "Red Hat CSAF VEX",
      "status": "final",
      "title": "kernel: netfilter: nf_log: validate MAC header was set before dumping it",
      "url": "https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-52942.json",
      "version": "3"
    }
  }
}



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Forecast uses a logistic model when the trend is rising, or an exponential decay model when the trend is falling. Fitted via linearized least squares.

Sightings

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Nomenclature

  • Seen: The vulnerability was mentioned, discussed, or observed by the user.
  • Confirmed: The vulnerability has been validated from an analyst's perspective.
  • Published Proof of Concept: A public proof of concept is available for this vulnerability.
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  • Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
  • Not confirmed: The user expressed doubt about the validity of the vulnerability.
  • Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.



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Vulnerabilities whose description is nearest to this one in the vector space of the CIRCL/vulnerability-attack-technique-biencoder model. This is a similarity search over the bi-encoder space (plain cosine), not a classification, and it has no measured accuracy.