netfilter: nf_conntrack_reasm: guard mac_header adjustment after IPv6 defrag

MITRE NVD CVE.ORG JSON API

Summary

CVECVE-2026-72250
StatePUBLISHED
AssignerLinux
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-08-15 06:21:52 UTC
Updated2026-08-17 06:18:27 UTC
DescriptionIn 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.

Risk And Classification

Primary CVSS: v3.1 7.8 HIGH from 416baaa9-dc9f-4396-8d5f-8c081fb06d67

CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

EPSS: 0.001640000 probability, percentile 0.060850000 (date 2026-08-17)

VersionSourceTypeScoreSeverityVector
3.1416baaa9-dc9f-4396-8d5f-8c081fb06d67Secondary7.8HIGHCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
3.1CNADECLARED7.8HIGHCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

CVSS v3.1 Breakdown

Attack Vector
Local
Attack Complexity
Low
Privileges Required
Low
User Interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
High

CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA Linux Linux affected 9fb9cbb1082d6b31fb45aa1a14432449a0df6cf1 6e8cd710ca35c576f5f2e5a396047c9ac61f75e5 git Not specified
CNA Linux Linux affected 9fb9cbb1082d6b31fb45aa1a14432449a0df6cf1 2a95ec21824a8ad81ad660b12231456fc0ac9830 git Not specified
CNA Linux Linux affected 9fb9cbb1082d6b31fb45aa1a14432449a0df6cf1 bbcdef2061b170af45702ce6b359c02c12acfc94 git Not specified
CNA Linux Linux affected 9fb9cbb1082d6b31fb45aa1a14432449a0df6cf1 cd0d7bbc027b4d3329712cdcdeb4e5567ffd0d58 git Not specified
CNA Linux Linux affected 9fb9cbb1082d6b31fb45aa1a14432449a0df6cf1 53ef70a315420ed31581d38343684b3bf9a3c76d git Not specified
CNA Linux Linux affected 9fb9cbb1082d6b31fb45aa1a14432449a0df6cf1 a58230f3a7c4f6c3261786bc1efb72c42e68cd25 git Not specified
CNA Linux Linux affected 9fb9cbb1082d6b31fb45aa1a14432449a0df6cf1 00bdce2fda7e430d24cfbc96764a1b96deb31f82 git Not specified
CNA Linux Linux affected 9fb9cbb1082d6b31fb45aa1a14432449a0df6cf1 3b08fed5b7e0d5e3a25d73ef3ba09cd33ade16c9 git Not specified
CNA Linux Linux affected 2.6.15 Not specified
CNA Linux Linux unaffected 2.6.15 semver Not specified
CNA Linux Linux unaffected 5.10.261 5.10.* semver Not specified
CNA Linux Linux unaffected 5.15.212 5.15.* semver Not specified
CNA Linux Linux unaffected 6.1.178 6.1.* semver Not specified
CNA Linux Linux unaffected 6.6.145 6.6.* semver Not specified
CNA Linux Linux unaffected 6.12.97 6.12.* semver Not specified
CNA Linux Linux unaffected 6.18.40 6.18.* semver Not specified
CNA Linux Linux unaffected 7.1.5 7.1.* semver Not specified
CNA Linux Linux unaffected 7.2 * original_commit_for_fix Not specified

References

ReferenceSourceLinkTags
git.kernel.org/stable/c/a58230f3a7c4f6c3261786bc1efb72c42e68cd25 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/53ef70a315420ed31581d38343684b3bf9a3c76d 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/6e8cd710ca35c576f5f2e5a396047c9ac61f75e5 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/3b08fed5b7e0d5e3a25d73ef3ba09cd33ade16c9 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/cd0d7bbc027b4d3329712cdcdeb4e5567ffd0d58 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/00bdce2fda7e430d24cfbc96764a1b96deb31f82 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/bbcdef2061b170af45702ce6b359c02c12acfc94 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/2a95ec21824a8ad81ad660b12231456fc0ac9830 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
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