--- id: CVE-2026-52942 title: |- 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-… 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-… severity: high cvss: 7.1 cvssVector: 'CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:H' cwe: - CWE-125 vendor: linux product: linux_kernel affected: - 'linux_kernel >= 2.6.36, < 5.15.210' - 'linux_kernel >= 5.16, < 6.1.176' - 'linux_kernel >= 6.2, < 6.6.143' - 'linux_kernel >= 6.7, < 6.12.94' - 'linux_kernel >= 6.13, < 6.18.36' - 'linux_kernel >= 6.19, < 7.0.13' - linux_kernel = 7.1 patched: - linux_kernel 7.0.13 published: '2026-06-24' updated: '2026-09-08' sourceUpdated: '2026-09-08T09:18:11.710' source: NVD sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2026-52942' references: - url: 'https://git.kernel.org/stable/c/2e96e1bc9b4d5450e6c33f078e19a9bc1dda6c0b' label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67 - url: 'https://git.kernel.org/stable/c/65ef7397eb9a296e91839f5fd10be96f23d332e7' label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67 - url: 'https://git.kernel.org/stable/c/8a81e336da685423f5b64aac4d571e63d674c52a' label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67 - url: 'https://git.kernel.org/stable/c/a84b6fedbc97078788be78dbdd7517d143ad1a77' label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67 - url: 'https://git.kernel.org/stable/c/af1b7699466f6556b351fa25d3dc870abfb5d310' label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67 - url: 'https://git.kernel.org/stable/c/befb8968a2abdfa948d5600ea7f7a509a292a590' label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67 - url: 'https://git.kernel.org/stable/c/c38d41134085193efd5b237cf513ad5b3421a60d' label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67 - url: 'https://git.kernel.org/stable/c/d704ee9c7bc68a161684c51a7ac05b446dcf38d4' label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67 - url: 'https://cert-portal.siemens.com/productcert/html/ssa-019113.html' label: 0b142b55-0307-4c5a-b3c9-f314f3fb7c5e - url: >- https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-52942.json - url: 'https://access.redhat.com/security/cve/CVE-2026-52942' - url: 'https://bugzilla.redhat.com/show_bug.cgi?id=2492091' - url: 'https://www.cve.org/CVERecord?id=CVE-2026-52942' - url: 'https://nvd.nist.gov/vuln/detail/CVE-2026-52942' - url: >- https://lore.kernel.org/linux-cve-announce/2026062435-CVE-2026-52942-2530@gregkh/T - url: 'https://access.redhat.com/errata/RHSA-2026:66325' - url: 'https://access.redhat.com/errata/RHSA-2026:66324' tags: - nvd - cve.org - csaf - vex - red-hat epss: 0.00128 epssPercentile: 0.02034 ingestedAt: '2026-09-08T13:33:25.159Z' scores: nvd: 7.1 vendor: 7 --- ## Overview 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) ## Affected - `linux_kernel >= 2.6.36, < 5.15.210` - `linux_kernel >= 5.16, < 6.1.176` - `linux_kernel >= 6.2, < 6.6.143` - `linux_kernel >= 6.7, < 6.12.94` - `linux_kernel >= 6.13, < 6.18.36` - `linux_kernel >= 6.19, < 7.0.13` - `linux_kernel = 7.1` ## Remediation Upgrade past the affected range: - `linux_kernel 7.0.13` ## Vendor advisories - **RHSA-2026:66325** · Red Hat · fixed in: Red Hat Enterprise Linux BaseOS (v. 8), Red Hat Enterprise Linux CRB (v. 8) · released 2026-09-10 · [advisory](https://access.redhat.com/errata/RHSA-2026:66325) - **RHSA-2026:66324** · Red Hat · fixed in: Red Hat Enterprise Linux NFV (v. 8), Red Hat Enterprise Linux RT (v. 8) · released 2026-09-10 · [advisory](https://access.redhat.com/errata/RHSA-2026:66324) - **Red Hat VEX** · Moderate · affected: Red Hat Enterprise Linux 10, Red Hat Enterprise Linux 9 · no fix planned: Red Hat Enterprise Linux 10, Red Hat Enterprise Linux 9 · updated 2026-09-10 · [vex](https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-52942.json)