EUVD-2026-38712
GHSA-3p98-fq5j-wx55
Severity by source
AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:H
Local CAP_NET_RAW gives PR:L; leaked bytes go to the kernel log so C:L not C:H; primary real impact is a slab OOB fault/DoS, hence A:H, no integrity impact.
Primary rating from Vendor (Linux).
CVSS VectorVendor: Linux
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:H
Lifecycle Timeline
5DescriptionCVE.org
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)
AnalysisAI
Out-of-bounds kernel memory read in the Linux kernel netfilter netdev logger (nf_log_syslog) lets a local low-privileged attacker leak adjacent slab memory into the kernel log and potentially crash the system. The flaw is in dump_mac_header(), whose fallback path tests skb->mac_header != skb->network_header but omits skb_mac_header_was_set(); an unset MAC header (value 0xffff) passes the check and causes a read ~64 KiB past the skb buffer. …
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Attack ChainAIDerived
Hypothetical attack flow derived from CVE metadata
Vulnerability AssessmentAI
| Exploitation | Exploitation requires three concrete prerequisites taken from the description: (1) the host must have an nftables netdev-family chain containing a 'log' action whose path reaches nf_log_unknown_packet()/dump_mac_header(); (2) the attacker must be able to create an AF_PACKET socket (typically CAP_NET_RAW) and set the PACKET_QDISC_BYPASS option; and (3) the packet must be sent so it reaches the egress nf_hook with mac_header still unset, which PACKET_QDISC_BYPASS achieves by skipping __dev_queue_xmit(). … Additional conditions and limiting factors are described in the full assessment. |
| Risk Assessment | Signals are consistent and point to a moderate, locally-scoped issue rather than an urgent priority. … Full risk analysis with EPSS, KEV, and SSVC signal comparison available after sign-in. |
| Exploit Scenario | A local user (or compromised container with CAP_NET_RAW) on a host that has an nftables netdev egress chain with a log rule opens an AF_PACKET socket, enables PACKET_QDISC_BYPASS, and transmits a crafted frame so it hits the egress hook with the MAC header unset. The logger then reads up to dev->hard_header_len bytes past the skb into the kernel log, disclosing adjacent slab memory and risking a slab-out-of-bounds fault/crash. … |
| Remediation | Vendor-released patch: upgrade to a fixed stable kernel for your series - 5.15.210, 6.1.176, 6.6.143, 6.12.94, 6.18.36, or 7.0.13/7.1 - or apply the corresponding stable commits listed at git.kernel.org (e.g., https://git.kernel.org/stable/c/d704ee9c7bc68a161684c51a7ac05b446dcf38d4) via your distribution's kernel update. … Detailed patch versions, workarounds, and compensating controls in full report. |
Recommended ActionAI
24 hours: Identify systems running vulnerable kernel versions (5.15 prior to 5.15.210; 6.1 prior to 6.1.176; 6.6 prior to 6.6.143; 6.12 prior to 6.12.94; 6.18 prior to 6.18.36; 7.0-7.1 prior to 7.0.13/7.1). …
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Same weakness CWE-125 – Out-of-bounds Read
View allSame technique Buffer Overflow
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External POC / Exploit Code
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