{"id":"CVE-2026-52942","state":"PUBLISHED","title":"netfilter: nf_log: validate MAC header was set before dumping it","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)","publishedAt":"2026-06-24T07:14:30.610Z","updatedAt":"2026-10-19T19:47:08.584Z","severity":{"score":7.1,"label":"High","version":"3.1","vector":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:H","source":"Linux"},"assigner":"Linux","products":["Linux Linux"],"affected":[{"vendor":"Linux","product":"Linux","defaultStatus":"unaffected","versions":[{"version":"7eb9282cd0efac08b8377cbd5037ba297c77e3f7","status":"affected","lessThan":"2e96e1bc9b4d5450e6c33f078e19a9bc1dda6c0b","versionType":"git"},{"version":"7eb9282cd0efac08b8377cbd5037ba297c77e3f7","status":"affected","lessThan":"d704ee9c7bc68a161684c51a7ac05b446dcf38d4","versionType":"git"},{"version":"7eb9282cd0efac08b8377cbd5037ba297c77e3f7","status":"affected","lessThan":"befb8968a2abdfa948d5600ea7f7a509a292a590","versionType":"git"},{"version":"7eb9282cd0efac08b8377cbd5037ba297c77e3f7","status":"affected","lessThan":"8a81e336da685423f5b64aac4d571e63d674c52a","versionType":"git"},{"version":"7eb9282cd0efac08b8377cbd5037ba297c77e3f7","status":"affected","lessThan":"c38d41134085193efd5b237cf513ad5b3421a60d","versionType":"git"},{"version":"7eb9282cd0efac08b8377cbd5037ba297c77e3f7","status":"affected","lessThan":"af1b7699466f6556b351fa25d3dc870abfb5d310","versionType":"git"},{"version":"7eb9282cd0efac08b8377cbd5037ba297c77e3f7","status":"affected","lessThan":"65ef7397eb9a296e91839f5fd10be96f23d332e7","versionType":"git"},{"version":"7eb9282cd0efac08b8377cbd5037ba297c77e3f7","status":"affected","lessThan":"a84b6fedbc97078788be78dbdd7517d143ad1a77","versionType":"git"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["net/netfilter/nf_log_syslog.c"]},{"vendor":"Linux","product":"Linux","defaultStatus":"affected","versions":[{"version":"2.6.36","status":"affected"},{"version":"0","status":"unaffected","lessThan":"2.6.36","versionType":"semver"},{"version":"5.10.261","status":"unaffected","lessThanOrEqual":"5.10.*","versionType":"semver"},{"version":"5.15.210","status":"unaffected","lessThanOrEqual":"5.15.*","versionType":"semver"},{"version":"6.1.176","status":"unaffected","lessThanOrEqual":"6.1.*","versionType":"semver"},{"version":"6.6.143","status":"unaffected","lessThanOrEqual":"6.6.*","versionType":"semver"},{"version":"6.12.94","status":"unaffected","lessThanOrEqual":"6.12.*","versionType":"semver"},{"version":"6.18.36","status":"unaffected","lessThanOrEqual":"6.18.*","versionType":"semver"},{"version":"7.0.13","status":"unaffected","lessThanOrEqual":"7.0.*","versionType":"semver"},{"version":"7.1","status":"unaffected","lessThanOrEqual":"*","versionType":"original_commit_for_fix"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["net/netfilter/nf_log_syslog.c"]}],"references":["https://git.kernel.org/stable/c/2e96e1bc9b4d5450e6c33f078e19a9bc1dda6c0b","https://git.kernel.org/stable/c/d704ee9c7bc68a161684c51a7ac05b446dcf38d4","https://git.kernel.org/stable/c/befb8968a2abdfa948d5600ea7f7a509a292a590","https://git.kernel.org/stable/c/8a81e336da685423f5b64aac4d571e63d674c52a","https://git.kernel.org/stable/c/c38d41134085193efd5b237cf513ad5b3421a60d","https://git.kernel.org/stable/c/af1b7699466f6556b351fa25d3dc870abfb5d310","https://git.kernel.org/stable/c/65ef7397eb9a296e91839f5fd10be96f23d332e7","https://git.kernel.org/stable/c/a84b6fedbc97078788be78dbdd7517d143ad1a77","https://cert-portal.siemens.com/productcert/html/ssa-019113.html","https://cert-portal.siemens.com/productcert/html/ssa-457936.html","https://cert-portal.siemens.com/productcert/html/ssa-784472.html"],"weaknesses":["CWE-125"],"ingestedAt":"2026-10-29T20:12:16.098Z","source":{"repository":"CVEProject/cvelistV5","path":"cves/2026/52xxx/CVE-2026-52942.json","commit":"556c9d3a8cd17e218bb8e452ba7cd619a384ff47"},"raw":{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2026-52942","state":"PUBLISHED","datePublished":"2026-06-24T07:14:30.610Z","dateUpdated":"2026-10-19T19:47:08.584Z","assignerShortName":"Linux","assignerOrgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","dateReserved":"2026-06-09T07:44:35.370Z"},"containers":{"cna":{"title":"netfilter: nf_log: validate MAC header was set before dumping it","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->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)"}],"affected":[{"vendor":"Linux","product":"Linux","defaultStatus":"unaffected","versions":[{"version":"7eb9282cd0efac08b8377cbd5037ba297c77e3f7","status":"affected","lessThan":"2e96e1bc9b4d5450e6c33f078e19a9bc1dda6c0b","versionType":"git"},{"version":"7eb9282cd0efac08b8377cbd5037ba297c77e3f7","status":"affected","lessThan":"d704ee9c7bc68a161684c51a7ac05b446dcf38d4","versionType":"git"},{"version":"7eb9282cd0efac08b8377cbd5037ba297c77e3f7","status":"affected","lessThan":"befb8968a2abdfa948d5600ea7f7a509a292a590","versionType":"git"},{"version":"7eb9282cd0efac08b8377cbd5037ba297c77e3f7","status":"affected","lessThan":"8a81e336da685423f5b64aac4d571e63d674c52a","versionType":"git"},{"version":"7eb9282cd0efac08b8377cbd5037ba297c77e3f7","status":"affected","lessThan":"c38d41134085193efd5b237cf513ad5b3421a60d","versionType":"git"},{"version":"7eb9282cd0efac08b8377cbd5037ba297c77e3f7","status":"affected","lessThan":"af1b7699466f6556b351fa25d3dc870abfb5d310","versionType":"git"},{"version":"7eb9282cd0efac08b8377cbd5037ba297c77e3f7","status":"affected","lessThan":"65ef7397eb9a296e91839f5fd10be96f23d332e7","versionType":"git"},{"version":"7eb9282cd0efac08b8377cbd5037ba297c77e3f7","status":"affected","lessThan":"a84b6fedbc97078788be78dbdd7517d143ad1a77","versionType":"git"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["net/netfilter/nf_log_syslog.c"]},{"vendor":"Linux","product":"Linux","defaultStatus":"affected","versions":[{"version":"2.6.36","status":"affected"},{"version":"0","status":"unaffected","lessThan":"2.6.36","versionType":"semver"},{"version":"5.10.261","status":"unaffected","lessThanOrEqual":"5.10.*","versionType":"semver"},{"version":"5.15.210","status":"unaffected","lessThanOrEqual":"5.15.*","versionType":"semver"},{"version":"6.1.176","status":"unaffected","lessThanOrEqual":"6.1.*","versionType":"semver"},{"version":"6.6.143","status":"unaffected","lessThanOrEqual":"6.6.*","versionType":"semver"},{"version":"6.12.94","status":"unaffected","lessThanOrEqual":"6.12.*","versionType":"semver"},{"version":"6.18.36","status":"unaffected","lessThanOrEqual":"6.18.*","versionType":"semver"},{"version":"7.0.13","status":"unaffected","lessThanOrEqual":"7.0.*","versionType":"semver"},{"version":"7.1","status":"unaffected","lessThanOrEqual":"*","versionType":"original_commit_for_fix"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["net/netfilter/nf_log_syslog.c"]}],"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"}],"metrics":[{"cvssV3_1":{"version":"3.1","vectorString":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:H","baseScore":7.1,"baseSeverity":"HIGH"},"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->head and prints them into the kernel log, creating a repeatable kernel memory disclosure primitive. Although each log entry is bounded by dev->hard_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":{"shortName":"Linux","orgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","dateUpdated":"2026-08-05T12:31:54.446Z"},"cpeApplicability":[{"nodes":[{"operator":"OR","negate":false,"cpeMatch":[{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"2.6.36","versionEndExcluding":"5.10.261"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"2.6.36","versionEndExcluding":"5.15.210"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"2.6.36","versionEndExcluding":"6.1.176"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"2.6.36","versionEndExcluding":"6.6.143"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"2.6.36","versionEndExcluding":"6.12.94"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"2.6.36","versionEndExcluding":"6.18.36"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"2.6.36","versionEndExcluding":"7.0.13"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"2.6.36","versionEndExcluding":"7.1"}]}]}],"x_generator":{"engine":"bippy-1.2.0"}},"adp":[{"affected":[{"vendor":"Siemens","product":"SIMATIC S7-1500 CPU 1518-4 PN/DP MFP","defaultStatus":"unknown","versions":[{"version":"V3.1.6","status":"affected","lessThan":"*","versionType":"custom"}]},{"vendor":"Siemens","product":"SIMATIC S7-1500 CPU 1518-4 PN/DP MFP","defaultStatus":"unknown","versions":[{"version":"V3.1.7","status":"affected","lessThan":"*","versionType":"custom"}]},{"vendor":"Siemens","product":"SIMATIC S7-1500 CPU 1518-4 PN/DP MFP","defaultStatus":"unknown","versions":[{"version":"V3.1.6","status":"affected","lessThan":"*","versionType":"custom"}]},{"vendor":"Siemens","product":"SIMATIC S7-1500 CPU 1518-4 PN/DP MFP","defaultStatus":"unknown","versions":[{"version":"V3.1.7","status":"affected","lessThan":"*","versionType":"custom"}]},{"vendor":"Siemens","product":"SIMATIC S7-1500 CPU 1518F-4 PN/DP MFP","defaultStatus":"unknown","versions":[{"version":"V3.1.6","status":"affected","lessThan":"*","versionType":"custom"}]},{"vendor":"Siemens","product":"SIMATIC S7-1500 CPU 1518F-4 PN/DP MFP","defaultStatus":"unknown","versions":[{"version":"V3.1.7","status":"affected","lessThan":"*","versionType":"custom"}]},{"vendor":"Siemens","product":"SIMATIC S7-1500 CPU 1518F-4 PN/DP MFP","defaultStatus":"unknown","versions":[{"version":"V3.1.6","status":"affected","lessThan":"*","versionType":"custom"}]},{"vendor":"Siemens","product":"SIMATIC S7-1500 CPU 1518F-4 PN/DP MFP","defaultStatus":"unknown","versions":[{"version":"V3.1.7","status":"affected","lessThan":"*","versionType":"custom"}]},{"vendor":"Siemens","product":"SIMATIC S7-1500 TM MFP - GNU/Linux subsystem","defaultStatus":"unknown","versions":[{"version":"0","status":"affected","lessThan":"*","versionType":"custom"}]},{"vendor":"Siemens","product":"SIPLUS S7-1500 CPU 1518-4 PN/DP MFP","defaultStatus":"unknown","versions":[{"version":"V3.1.6","status":"affected","lessThan":"*","versionType":"custom"}]},{"vendor":"Siemens","product":"SIPLUS S7-1500 CPU 1518-4 PN/DP MFP","defaultStatus":"unknown","versions":[{"version":"V3.1.7","status":"affected","lessThan":"*","versionType":"custom"}]}],"references":[{"url":"https://cert-portal.siemens.com/productcert/html/ssa-019113.html"},{"url":"https://cert-portal.siemens.com/productcert/html/ssa-457936.html"},{"url":"https://cert-portal.siemens.com/productcert/html/ssa-784472.html"}],"providerMetadata":{"shortName":"siemens-SADP","orgId":"0b142b55-0307-4c5a-b3c9-f314f3fb7c5e","dateUpdated":"2026-10-15T01:21:57.901Z"},"x_adpType":"supplier"},{"title":"CISA ADP Vulnrichment","metrics":[{"other":{"type":"ssvc","content":{"id":"CVE-2026-52942","role":"CISA Coordinator","options":[{"Exploitation":"none"},{"Automatable":"no"},{"Technical Impact":"partial"}],"version":"2.0.3","timestamp":"2026-10-16T15:23:04.866965Z"}}}],"problemTypes":[{"descriptions":[{"cweId":"CWE-125","lang":"en","type":"CWE","description":"CWE-125 Out-of-bounds Read"}]}],"providerMetadata":{"shortName":"CISA-ADP","orgId":"134c704f-9b21-4f2e-91b3-4a467353bcc0","dateUpdated":"2026-10-19T19:47:08.584Z"}}]}}}