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.
CVSS Details
- CVSS 3.1 Base Score: 7.8
- CVSS 3.1 Vector: (CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H)
Covered by Rapid7
| Product | Vendor Advisory | Solution File | Added | Published |
|---|---|---|---|---|
| Amazon_linux_2023 | — | Upgrade kernel-debuginfo-common-aarch64Upgrade perfUpgrade bpftoolUpgrade bpftool-debuginfoUpgrade kernel-modules-extra-commonUpgrade kernel-toolsUpgrade perf-debuginfoUpgrade python3-perf-debuginfoUpgrade kernelUpgrade kernel-debuginfoUpgrade kernel-headersUpgrade kernel-modules-extraUpgrade kernel-develUpgrade kernel-debuginfo-common-x86_64Upgrade python3-perfUpgrade kernel-tools-debuginfoUpgrade kernel-tools-develUpgrade kernel-livepatch-6.1.180-225.360 | Sep 1, 2026 | Aug 15, 2026 |
| Debian | — | Upgrade linux | Aug 16, 2026 | Aug 16, 2026 |
| Redhat_linux | — | No solution exists | Aug 20, 2026 | Aug 15, 2026 |
| Vmware Photon_os | — | Use 'tdnf update' to upgrade all packages to the latest version. | Aug 25, 2026 | Aug 15, 2026 |
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