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netfilter: nf_conntrack_reasm: guard mac_header adjustment after IPv6 defrag

Type: advisorySource: Official CVE List1 source record

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.

Announced Source revision 1
Original source ↗

CVE-2026-72250

Primary source · Revision 1

Imported from structured advisory data. Source references identify upstream records or fields; verify affected versions and your deployed configuration.

Security context

Source reference: cve:CVE-2026-72250

Linux

Source reference: /containers/cna/affected/0/product

Affected versions
Not stated in this record
Fixed versions
Not stated in this record
Prerequisites
Not stated in this record

Linux

Source reference: /containers/cna/affected/1/product

Affected versions
Not stated in this record
Fixed versions
Not stated in this record
Prerequisites
Not stated in this record

Structured affected-version data

Original package identities and version rules from this source.

[
  {
    "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
    "vendor": "Linux",
    "product": "Linux",
    "versions": [
      {
        "status": "affected",
        "version": "9fb9cbb1082d6b31fb45aa1a14432449a0df6cf1",
        "lessThan": "6e8cd710ca35c576f5f2e5a396047c9ac61f75e5",
        "versionType": "git"
      },
      {
        "status": "affected",
        "version": "9fb9cbb1082d6b31fb45aa1a14432449a0df6cf1",
        "lessThan": "2a95ec21824a8ad81ad660b12231456fc0ac9830",
        "versionType": "git"
      },
      {
        "status": "affected",
        "version": "9fb9cbb1082d6b31fb45aa1a14432449a0df6cf1",
        "lessThan": "bbcdef2061b170af45702ce6b359c02c12acfc94",
        "versionType": "git"
      },
      {
        "status": "affected",
        "version": "9fb9cbb1082d6b31fb45aa1a14432449a0df6cf1",
        "lessThan": "cd0d7bbc027b4d3329712cdcdeb4e5567ffd0d58",
        "versionType": "git"
      },
      {
        "status": "affected",
        "version": "9fb9cbb1082d6b31fb45aa1a14432449a0df6cf1",
        "lessThan": "53ef70a315420ed31581d38343684b3bf9a3c76d",
        "versionType": "git"
      },
      {
        "status": "affected",
        "version": "9fb9cbb1082d6b31fb45aa1a14432449a0df6cf1",
        "lessThan": "a58230f3a7c4f6c3261786bc1efb72c42e68cd25",
        "versionType": "git"
      },
      {
        "status": "affected",
        "version": "9fb9cbb1082d6b31fb45aa1a14432449a0df6cf1",
        "lessThan": "00bdce2fda7e430d24cfbc96764a1b96deb31f82",
        "versionType": "git"
      },
      {
        "status": "affected",
        "version": "9fb9cbb1082d6b31fb45aa1a14432449a0df6cf1",
        "lessThan": "3b08fed5b7e0d5e3a25d73ef3ba09cd33ade16c9",
        "versionType": "git"
      }
    ],
    "programFiles": [
      "net/ipv6/netfilter/nf_conntrack_reasm.c"
    ],
    "defaultStatus": "unaffected"
  },
  {
    "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
    "vendor": "Linux",
    "product": "Linux",
    "versions": [
      {
        "status": "affected",
        "version": "2.6.15"
      },
      {
        "status": "unaffected",
        "version": "0",
        "lessThan": "2.6.15",
        "versionType": "semver"
      },
      {
        "status": "unaffected",
        "version": "5.10.261",
        "versionType": "semver",
        "lessThanOrEqual": "5.10.*"
      },
      {
        "status": "unaffected",
        "version": "5.15.212",
        "versionType": "semver",
        "lessThanOrEqual": "5.15.*"
      },
      {
        "status": "unaffected",
        "version": "6.1.178",
        "versionType": "semver",
        "lessThanOrEqual": "6.1.*"
      },
      {
        "status": "unaffected",
        "version": "6.6.145",
        "versionType": "semver",
        "lessThanOrEqual": "6.6.*"
      },
      {
        "status": "unaffected",
        "version": "6.12.97",
        "versionType": "semver",
        "lessThanOrEqual": "6.12.*"
      },
      {
        "status": "unaffected",
        "version": "6.18.40",
        "versionType": "semver",
        "lessThanOrEqual": "6.18.*"
      },
      {
        "status": "unaffected",
        "version": "7.1.5",
        "versionType": "semver",
        "lessThanOrEqual": "7.1.*"
      },
      {
        "status": "unaffected",
        "version": "7.2",
        "versionType": "original_commit_for_fix",
        "lessThanOrEqual": "*"
      }
    ],
    "programFiles": [
      "net/ipv6/netfilter/nf_conntrack_reasm.c"
    ],
    "defaultStatus": "affected"
  }
]
Related CVEs
CVE-2026-72250

Source reference: /cveMetadata/cveId

Publisher severity

high

Source reference: /containers/cna/metrics

Event
#32994 · Revision 1
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Publisher date
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