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ip6_tunnel: clear skb2->cb[] in ip4ip6_err()

Type: advisorySource: Official CVE List1 source record

In the Linux kernel, the following vulnerability has been resolved: ip6_tunnel: clear skb2->cb[] in ip4ip6_err() Oskar Kjos reported the following problem. ip4ip6_err() calls icmp_send() on a cloned skb whose cb[] was written by the IPv6 receive path as struct inet6_skb_parm. icmp_send() passes IPCB(skb2) to __ip_options_echo(), which interprets that cb[] region as struct inet_skb_parm (IPv4). The layouts differ: inet6_skb_parm.nhoff at offset 14 overlaps inet_skb_parm.opt.rr, producing a non-zero rr value. __ip_options_echo() then reads optlen from attacker-controlled packet data at sptr[rr+1] and copies that many bytes into dopt->__data, a fixed 40-byte stack buffer (IP_OPTIONS_DATA_FIXED_SIZE). To fix this we clear skb2->cb[], as suggested by Oskar Kjos. Also add minimal IPv4 header validation (version == 4, ihl >= 5).

Announced Source revision 1
Original source ↗

CVE-2026-43037

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-2026-43037

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": "c4d3efafcc933fd2ffd169d7dc4f980393a13796",
        "lessThan": "ea9f65b27c8404e164848ebff1443310fd187629",
        "versionType": "git"
      },
      {
        "status": "affected",
        "version": "c4d3efafcc933fd2ffd169d7dc4f980393a13796",
        "lessThan": "d6621f60192fe10c047a4487be42a6f4c150707f",
        "versionType": "git"
      },
      {
        "status": "affected",
        "version": "c4d3efafcc933fd2ffd169d7dc4f980393a13796",
        "lessThan": "2cc6e3b0fe0f0242d1f530a93a4924f48ab85ba5",
        "versionType": "git"
      },
      {
        "status": "affected",
        "version": "c4d3efafcc933fd2ffd169d7dc4f980393a13796",
        "lessThan": "a0c4ce9900a108eaf55d0f3b399cb55999647d39",
        "versionType": "git"
      },
      {
        "status": "affected",
        "version": "c4d3efafcc933fd2ffd169d7dc4f980393a13796",
        "lessThan": "1063515ce15ff31065c4e7f8265f4c2fd3c54876",
        "versionType": "git"
      },
      {
        "status": "affected",
        "version": "c4d3efafcc933fd2ffd169d7dc4f980393a13796",
        "lessThan": "590f622669b97eaf7b57a1de7b0a6e68c5d8b2c3",
        "versionType": "git"
      },
      {
        "status": "affected",
        "version": "c4d3efafcc933fd2ffd169d7dc4f980393a13796",
        "lessThan": "4a622658f384b03560834cbe8ffcfe69a278f7c8",
        "versionType": "git"
      },
      {
        "status": "affected",
        "version": "c4d3efafcc933fd2ffd169d7dc4f980393a13796",
        "lessThan": "2edfa31769a4add828a7e604b21cb82aaaa05925",
        "versionType": "git"
      }
    ],
    "programFiles": [
      "net/ipv6/ip6_tunnel.c"
    ],
    "defaultStatus": "unaffected"
  },
  {
    "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
    "vendor": "Linux",
    "product": "Linux",
    "versions": [
      {
        "status": "affected",
        "version": "2.6.22"
      },
      {
        "status": "unaffected",
        "version": "0",
        "lessThan": "2.6.22",
        "versionType": "semver"
      },
      {
        "status": "unaffected",
        "version": "5.10.253",
        "versionType": "semver",
        "lessThanOrEqual": "5.10.*"
      },
      {
        "status": "unaffected",
        "version": "5.15.203",
        "versionType": "semver",
        "lessThanOrEqual": "5.15.*"
      },
      {
        "status": "unaffected",
        "version": "6.1.168",
        "versionType": "semver",
        "lessThanOrEqual": "6.1.*"
      },
      {
        "status": "unaffected",
        "version": "6.6.134",
        "versionType": "semver",
        "lessThanOrEqual": "6.6.*"
      },
      {
        "status": "unaffected",
        "version": "6.12.81",
        "versionType": "semver",
        "lessThanOrEqual": "6.12.*"
      },
      {
        "status": "unaffected",
        "version": "6.18.22",
        "versionType": "semver",
        "lessThanOrEqual": "6.18.*"
      },
      {
        "status": "unaffected",
        "version": "6.19.12",
        "versionType": "semver",
        "lessThanOrEqual": "6.19.*"
      },
      {
        "status": "unaffected",
        "version": "7.0",
        "versionType": "original_commit_for_fix",
        "lessThanOrEqual": "*"
      }
    ],
    "programFiles": [
      "net/ipv6/ip6_tunnel.c"
    ],
    "defaultStatus": "affected"
  }
]
Related CVEs
CVE-2026-43037

Source reference: /cveMetadata/cveId

Publisher severity

critical

Source reference: /containers/cna/metrics

Event
#40007 · Revision 1
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Publisher date
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