CVE-2026-72250
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.
How to fix
- Linux Linux6e8cd710ca35c576f5f2e5a396047c9ac61f75e5, 2a95ec21824a8ad81ad660b12231456fc0ac9830, bbcdef2061b170af45702ce6b359c02c12acfc94, cd0d7bbc027b4d3329712cdcdeb4e5567ffd0d58, 53ef70a315420ed31581d38343684b3bf9a3c76d, a58230f3a7c4f6c3261786bc1efb72c42e68cd25, 00bdce2fda7e430d24cfbc96764a1b96deb31f82, 3b08fed5b7e0d5e3a25d73ef3ba09cd33ade16c9 or later
Affected products
| Product | Affected versions | Fixed in |
|---|---|---|
| Linux Linux | 9fb9cbb1082d6b31fb45aa1a14432449a0df6cf1 ≤ v < 6e8cd710ca35c576f5f2e5a396047c9ac61f75e5, 9fb9cbb1082d6b31fb45aa1a14432449a0df6cf1 ≤ v < 2a95ec21824a8ad81ad660b12231456fc0ac9830, 9fb9cbb1082d6b31fb45aa1a14432449a0df6cf1 ≤ v < bbcdef2061b170af45702ce6b359c02c12acfc94, 9fb9cbb1082d6b31fb45aa1a14432449a0df6cf1 ≤ v < cd0d7bbc027b4d3329712cdcdeb4e5567ffd0d58, 9fb9cbb1082d6b31fb45aa1a14432449a0df6cf1 ≤ v < 53ef70a315420ed31581d38343684b3bf9a3c76d, 9fb9cbb1082d6b31fb45aa1a14432449a0df6cf1 ≤ v < a58230f3a7c4f6c3261786bc1efb72c42e68cd25, 9fb9cbb1082d6b31fb45aa1a14432449a0df6cf1 ≤ v < 00bdce2fda7e430d24cfbc96764a1b96deb31f82, 9fb9cbb1082d6b31fb45aa1a14432449a0df6cf1 ≤ v < 3b08fed5b7e0d5e3a25d73ef3ba09cd33ade16c9, 2.6.15 | 6e8cd710ca35c576f5f2e5a396047c9ac61f75e5, 2a95ec21824a8ad81ad660b12231456fc0ac9830, bbcdef2061b170af45702ce6b359c02c12acfc94, cd0d7bbc027b4d3329712cdcdeb4e5567ffd0d58, 53ef70a315420ed31581d38343684b3bf9a3c76d, a58230f3a7c4f6c3261786bc1efb72c42e68cd25, 00bdce2fda7e430d24cfbc96764a1b96deb31f82, 3b08fed5b7e0d5e3a25d73ef3ba09cd33ade16c9 |
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