GHSA-3P98-FQ5J-WX55
Vulnerability from github – Published: 2026-06-24 09:30 – Updated: 2026-09-08 09:35In 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": [],
"aliases": [
"CVE-2026-52942"
],
"database_specific": {
"cwe_ids": [
"CWE-125"
],
"github_reviewed": false,
"github_reviewed_at": null,
"nvd_published_at": "2026-06-24T08:16:24Z",
"severity": "HIGH"
},
"details": "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": "GHSA-3p98-fq5j-wx55",
"modified": "2026-09-08T09:35:31Z",
"published": "2026-06-24T09:30:49Z",
"references": [
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2026-52942"
},
{
"type": "WEB",
"url": "https://cert-portal.siemens.com/productcert/html/ssa-019113.html"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/2e96e1bc9b4d5450e6c33f078e19a9bc1dda6c0b"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/65ef7397eb9a296e91839f5fd10be96f23d332e7"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/8a81e336da685423f5b64aac4d571e63d674c52a"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/a84b6fedbc97078788be78dbdd7517d143ad1a77"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/af1b7699466f6556b351fa25d3dc870abfb5d310"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/befb8968a2abdfa948d5600ea7f7a509a292a590"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/c38d41134085193efd5b237cf513ad5b3421a60d"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/d704ee9c7bc68a161684c51a7ac05b446dcf38d4"
}
],
"schema_version": "1.4.0",
"severity": [
{
"score": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:H",
"type": "CVSS_V3"
}
]
}
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