In the Linux kernel, the following vulnerability has been resolved: netfilter: nf_conntrack_reasm: guard mac_header adjustment after IPv6 defrag nf_ct_frag6_reasm() slides the packet head forward to drop the IPv6 fragment header and then unconditionally advances skb->mac_header: skb->mac_header += sizeof(struct frag_hdr); On the NF_INET_LOCAL_OUT defrag path the skb has no link-layer header yet, so skb->mac_header is still the "not set" sentinel (u16)~0U. Adding sizeof(struct frag_hdr) wraps it to a small value (0xffff + 8 == 7), after which skb_mac_header_was_set() wrongly reports a MAC header is present and skb_mac_header() points into the headroom. The reassembler has done this unconditional add since it was introduced; it was harmless while mac_header was a bare pointer, but wrong once mac_header became a u16 offset whose unset state is the ~0U sentinel tested by skb_mac_header_was_set(). The sibling net/ipv6/reassembly.c does the same relocation and does guard the adjustment; mirror the guard here.

Metrics

No CVSS v4.0

No CVSS v3.1

No CVSS v3.0

No CVSS v2

This CVE is not in the KEV list.

No EPSS score available.

Key SSVC decision points have not yet been added.

Affected Vendors & Products

Vendors Products
Linux
  • Linux Kernel

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References
Link Providers
https://git.kernel.org/stable/c/00bdce2fda7e430d24cfbc96764a1b96deb31f82 cve-icon cve-icon
https://git.kernel.org/stable/c/2a95ec21824a8ad81ad660b12231456fc0ac9830 cve-icon cve-icon
https://git.kernel.org/stable/c/3b08fed5b7e0d5e3a25d73ef3ba09cd33ade16c9 cve-icon cve-icon
https://git.kernel.org/stable/c/53ef70a315420ed31581d38343684b3bf9a3c76d cve-icon cve-icon
https://git.kernel.org/stable/c/6e8cd710ca35c576f5f2e5a396047c9ac61f75e5 cve-icon cve-icon
https://git.kernel.org/stable/c/a58230f3a7c4f6c3261786bc1efb72c42e68cd25 cve-icon cve-icon
https://git.kernel.org/stable/c/bbcdef2061b170af45702ce6b359c02c12acfc94 cve-icon cve-icon
https://git.kernel.org/stable/c/cd0d7bbc027b4d3329712cdcdeb4e5567ffd0d58 cve-icon cve-icon
History

Sat, 15 Aug 2026 06:00:00 +0000

Type Values Removed Values Added
Description In the Linux kernel, the following vulnerability has been resolved: netfilter: nf_conntrack_reasm: guard mac_header adjustment after IPv6 defrag nf_ct_frag6_reasm() slides the packet head forward to drop the IPv6 fragment header and then unconditionally advances skb->mac_header: skb->mac_header += sizeof(struct frag_hdr); On the NF_INET_LOCAL_OUT defrag path the skb has no link-layer header yet, so skb->mac_header is still the "not set" sentinel (u16)~0U. Adding sizeof(struct frag_hdr) wraps it to a small value (0xffff + 8 == 7), after which skb_mac_header_was_set() wrongly reports a MAC header is present and skb_mac_header() points into the headroom. The reassembler has done this unconditional add since it was introduced; it was harmless while mac_header was a bare pointer, but wrong once mac_header became a u16 offset whose unset state is the ~0U sentinel tested by skb_mac_header_was_set(). The sibling net/ipv6/reassembly.c does the same relocation and does guard the adjustment; mirror the guard here.
Title netfilter: nf_conntrack_reasm: guard mac_header adjustment after IPv6 defrag
First Time appeared Linux
Linux linux Kernel
CPEs cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*
Vendors & Products Linux
Linux linux Kernel
References
cve-icon MITRE

Status: PUBLISHED

Assigner: Linux

Published:

Updated: 2026-08-15T05:54:39.134Z

Reserved: 2026-08-09T03:40:39.915Z

Link: CVE-2026-72250

cve-icon Vulnrichment

No data.

cve-icon NVD

Status : Received

Published: 2026-08-15T06:21:52.267

Modified: 2026-08-15T06:21:52.267

Link: CVE-2026-72250

cve-icon Redhat

No data.

cve-icon OpenCVE Enrichment

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