{
  "schemaVersion": 1,
  "attribution": [
    {
      "source": "CISA Known Exploited Vulnerabilities",
      "url": "https://www.cisa.gov/known-exploited-vulnerabilities-catalog",
      "licence": "US government work"
    },
    {
      "source": "GitHub Advisory Database",
      "url": "https://github.com/advisories",
      "licence": "CC BY 4.0"
    },
    {
      "source": "Have I Been Pwned",
      "url": "https://haveibeenpwned.com/",
      "licence": "CC BY 4.0"
    },
    {
      "source": "CVE Program (CVE records)",
      "url": "https://www.cve.org/Legal/TermsOfUse",
      "licence": "CVE Terms of Use",
      "notice": "Copyright © 1999-2026, The MITRE Corporation. CVE is a trademark and the CVE logo is a registered trademark of The MITRE Corporation.",
      "terms": "CVE Usage: MITRE hereby grants you a perpetual, worldwide, non-exclusive, no-charge, royalty-free, irrevocable copyright license to reproduce, prepare derivative works of, publicly display, publicly perform, sublicense, and distribute Common Vulnerabilities and Exposures (CVE™). Any copy you make for such purposes is authorized provided that you reproduce MITRE's copyright designation and this license in any such copy."
    },
    {
      "source": "FIRST EPSS",
      "url": "https://www.first.org/epss/",
      "licence": "free to use; FIRST requests attribution"
    }
  ],
  "record": {
    "id": "CVE-2021-47515",
    "sourceURL": "https://www.cve.org/CVERecord?id=CVE-2021-47515",
    "idYear": 2021,
    "status": "PUBLISHED",
    "publishedAt": "2024-05-24T15:09:29.334Z",
    "updatedAt": "2026-08-05T08:48:12.387Z",
    "importedAt": "2026-10-24T01:56:36.661Z",
    "snapshot": {
      "id": "cve_2026-10-24_midnight_baseline",
      "at": "2026-10-24T00:00:00.000Z",
      "source": "https://github.com/CVEProject/cvelistV5/releases/tag/cve_2026-10-24_0100Z"
    },
    "facts": {
      "title": "seg6: fix the iif in the IPv6 socket control block",
      "summary": "In the Linux kernel, the following vulnerability has been resolved:\n\nseg6: fix the iif in the IPv6 socket control block\n\nWhen an IPv4 packet is received, the ip_rcv_core(...) sets the receiving\ninterface index into the IPv4 socket control block (v5.16-rc4,\nnet/ipv4/ip_input.c line 510):\n\n    IPCB(skb)->iif = skb->skb_iif;\n\nIf that IPv4 packet is meant to be encapsulated in an outer IPv6+SRH\nheader, the seg6_do_srh_encap(...) performs the required encapsulation.\nIn this case, the seg6_do_srh_encap function clears the IPv6 socket control\nblock (v5.16-rc4 net/ipv6/seg6_iptunnel.c line 163):\n\n    memset(IP6CB(skb), 0, sizeof(*IP6CB(skb)));\n\nThe memset(...) was introduced in commit ef489749aae5 (\"ipv6: sr: clear\nIP6CB(skb) on SRH ip4ip6 encapsulation\") a long time ago (2019-01-29).\n\nSince the IPv6 socket control block and the IPv4 socket control block share\nthe same memory area (skb->cb), the receiving interface index info is lost\n(IP6CB(skb)->iif is set to zero).\n\nAs a side effect, that condition triggers a NULL pointer dereference if\ncommit 0857d6f8c759 (\"ipv6: When forwarding count rx stats on the orig\nnetdev\") is applied.\n\nTo fix that issue, we set the IP6CB(skb)->iif with the index of the\nreceiving interface once again.",
      "affected": [
        {
          "vendor": "Linux",
          "product": "Linux",
          "defaultStatus": "unaffected",
          "versions": [
            {
              "version": "c630ec8bdadae9d557b1ceb9d6c06e149108a0d4",
              "status": "affected",
              "versionType": "git",
              "lessThan": "b16d412e5f79734033df04e97d7ea2f50a8e9fe3"
            },
            {
              "version": "2f704348c93ff8119e642dae6a72327f90b82810",
              "status": "affected",
              "versionType": "git",
              "lessThan": "6431e71093f3da586a00c6d931481ffb0dc2db0e"
            },
            {
              "version": "ef489749aae508e6f17886775c075f12ff919fb1",
              "status": "affected",
              "versionType": "git",
              "lessThan": "ef8804e47c0a44ae106ead1740408af5ea6c6ee9"
            },
            {
              "version": "ef489749aae508e6f17886775c075f12ff919fb1",
              "status": "affected",
              "versionType": "git",
              "lessThan": "666521b3852d2b2f52d570f9122b1e4b50d96831"
            },
            {
              "version": "ef489749aae508e6f17886775c075f12ff919fb1",
              "status": "affected",
              "versionType": "git",
              "lessThan": "98adb2bbfa407c9290bda299d4c6f7a1c4ebd5e1"
            },
            {
              "version": "ef489749aae508e6f17886775c075f12ff919fb1",
              "status": "affected",
              "versionType": "git",
              "lessThan": "ae68d93354e5bf5191ee673982251864ea24dd5c"
            },
            {
              "version": "b71b7e0280f47b4ac633fbfd153423814ea87810",
              "status": "affected",
              "versionType": "git"
            },
            {
              "version": "4.14.98",
              "status": "affected",
              "versionType": "semver",
              "lessThan": "4.14.258"
            },
            {
              "version": "4.19.20",
              "status": "affected",
              "versionType": "semver",
              "lessThan": "4.19.221"
            },
            {
              "version": "4.20.7",
              "status": "affected",
              "versionType": "semver",
              "lessThan": "4.21"
            }
          ]
        },
        {
          "vendor": "Linux",
          "product": "Linux",
          "defaultStatus": "affected",
          "versions": [
            {
              "version": "5.0",
              "status": "affected"
            },
            {
              "version": "0",
              "status": "unaffected",
              "versionType": "semver",
              "lessThan": "5.0"
            },
            {
              "version": "4.14.258",
              "status": "unaffected",
              "versionType": "semver",
              "lessThanOrEqual": "4.14.*"
            },
            {
              "version": "4.19.221",
              "status": "unaffected",
              "versionType": "semver",
              "lessThanOrEqual": "4.19.*"
            },
            {
              "version": "5.4.165",
              "status": "unaffected",
              "versionType": "semver",
              "lessThanOrEqual": "5.4.*"
            },
            {
              "version": "5.10.85",
              "status": "unaffected",
              "versionType": "semver",
              "lessThanOrEqual": "5.10.*"
            },
            {
              "version": "5.15.8",
              "status": "unaffected",
              "versionType": "semver",
              "lessThanOrEqual": "5.15.*"
            },
            {
              "version": "5.16",
              "status": "unaffected",
              "versionType": "original_commit_for_fix",
              "lessThanOrEqual": "*"
            }
          ]
        }
      ]
    }
  }
}