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CVE-2026-72250

netfilter: nf_conntrack_reasm: guard mac_header adjustment after IPv6 defrag

Published
Last modified
published
Not listed in CISA KEV
Fix
Fixed in 5.10.261, 5.15.212, 6.1.178, 6.6.145, 6.12.97, and 2 more
None on Exploit-DB, Metasploit or GitHub
  • Exploitation: none
  • Automatable: no
  • Technical impact: total

Summary

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.

Timeline

  1. CVE published
  2. CISA SSVC assessment

    Exploitation: none · Automatable: no · Technical impact: total

  3. Record last updated

Affected versions

  • Linux Linux

    From 9fb9cbb1082d6b31fb45aa1a14432449a0df6cf1 · fixed in 6e8cd710ca35c576f5f2e5a396047c9ac61f75e5; From 9fb9cbb1082d6b31fb45aa1a14432449a0df6cf1 · fixed in 2a95ec21824a8ad81ad660b12231456fc0ac9830; From 9fb9cbb1082d6b31fb45aa1a14432449a0df6cf1 · fixed in bbcdef2061b170af45702ce6b359c02c12acfc94; From 9fb9cbb1082d6b31fb45aa1a14432449a0df6cf1 · fixed in cd0d7bbc027b4d3329712cdcdeb4e5567ffd0d58; From 9fb9cbb1082d6b31fb45aa1a14432449a0df6cf1 · fixed in 53ef70a315420ed31581d38343684b3bf9a3c76d; From 9fb9cbb1082d6b31fb45aa1a14432449a0df6cf1 · fixed in a58230f3a7c4f6c3261786bc1efb72c42e68cd25; From 9fb9cbb1082d6b31fb45aa1a14432449a0df6cf1 · fixed in 00bdce2fda7e430d24cfbc96764a1b96deb31f82; From 9fb9cbb1082d6b31fb45aa1a14432449a0df6cf1 · fixed in 3b08fed5b7e0d5e3a25d73ef3ba09cd33ade16c9

  • Linux Linux

    2.6.15

  • KernelLinux

    From 2.6.15 · fixed in 5.10.261; From 5.11.0 · fixed in 5.15.212; From 5.16.0 · fixed in 6.1.178; From 6.2.0 · fixed in 6.6.145; From 6.7.0 · fixed in 6.12.97; From 6.13.0 · fixed in 6.18.40; From 6.19.0 · fixed in 7.1.5

References 8

git.kernel.org