{"id":"DEBIAN-CVE-2026-52942","details":"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-\u003emac_header != skb-\u003enetwork_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-\u003ehead + 0xffff, ~64 KiB past the buffer; the loop then reads dev-\u003ehard_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)","modified":"2026-09-09T08:47:31.145629776Z","published":"2026-06-24T08:16:24.490Z","upstream":["CVE-2026-52942"],"references":[{"type":"ADVISORY","url":"https://security-tracker.debian.org/tracker/CVE-2026-52942"}],"affected":[{"package":{"name":"linux","ecosystem":"Debian:12","purl":"pkg:deb/debian/linux?arch=source&distro=bookworm"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"6.1.176-1"}]}],"versions":["6.1.106-1","6.1.106-2","6.1.106-3","6.1.112-1","6.1.115-1","6.1.119-1","6.1.123-1","6.1.124-1","6.1.128-1","6.1.129-1","6.1.133-1","6.1.135-1","6.1.137-1","6.1.139-1","6.1.140-1","6.1.147-1","6.1.148-1","6.1.153-1","6.1.158-1","6.1.159-1","6.1.162-1","6.1.164-1","6.1.170-1","6.1.170-2","6.1.170-3","6.1.172-1","6.1.174-1","6.1.27-1","6.1.37-1","6.1.38-1","6.1.38-2","6.1.38-2~bpo11+1","6.1.38-3","6.1.38-4","6.1.38-4~bpo11+1","6.1.52-1","6.1.55-1","6.1.55-1~bpo11+1","6.1.64-1","6.1.66-1","6.1.67-1","6.1.69-1","6.1.69-1~bpo11+1","6.1.76-1","6.1.76-1~bpo11+1","6.1.82-1","6.1.85-1","6.1.90-1","6.1.90-1~bpo11+1","6.1.94-1","6.1.94-1~bpo11+1","6.1.98-1","6.1.99-1"],"ecosystem_specific":{"urgency":"not 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