{
  "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-2021-4454",
    "sourceURL": "https://www.cve.org/CVERecord?id=CVE-2021-4454",
    "idYear": 2021,
    "status": "PUBLISHED",
    "publishedAt": "2025-03-27T16:37:09.381Z",
    "updatedAt": "2026-10-15T21:21:06.266Z",
    "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": "can: j1939: fix errant WARN_ON_ONCE in j1939_session_deactivate",
      "summary": "In the Linux kernel, the following vulnerability has been resolved:\n\ncan: j1939: fix errant WARN_ON_ONCE in j1939_session_deactivate\n\nThe conclusion \"j1939_session_deactivate() should be called with a\nsession ref-count of at least 2\" is incorrect. In some concurrent\nscenarios, j1939_session_deactivate can be called with the session\nref-count less than 2. But there is not any problem because it\nwill check the session active state before session putting in\nj1939_session_deactivate_locked().\n\nHere is the concurrent scenario of the problem reported by syzbot\nand my reproduction log.\n\n        cpu0                            cpu1\n                                j1939_xtp_rx_eoma\nj1939_xtp_rx_abort_one\n                                j1939_session_get_by_addr [kref == 2]\nj1939_session_get_by_addr [kref == 3]\nj1939_session_deactivate [kref == 2]\nj1939_session_put [kref == 1]\n\t\t\t\tj1939_session_completed\n\t\t\t\tj1939_session_deactivate\n\t\t\t\tWARN_ON_ONCE(kref < 2)\n\n=====================================================\nWARNING: CPU: 1 PID: 21 at net/can/j1939/transport.c:1088 j1939_session_deactivate+0x5f/0x70\nCPU: 1 PID: 21 Comm: ksoftirqd/1 Not tainted 5.14.0-rc7+ #32\nHardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.13.0-1ubuntu1 04/01/2014\nRIP: 0010:j1939_session_deactivate+0x5f/0x70\nCall Trace:\n j1939_session_deactivate_activate_next+0x11/0x28\n j1939_xtp_rx_eoma+0x12a/0x180\n j1939_tp_recv+0x4a2/0x510\n j1939_can_recv+0x226/0x380\n can_rcv_filter+0xf8/0x220\n can_receive+0x102/0x220\n ? process_backlog+0xf0/0x2c0\n can_rcv+0x53/0xf0\n __netif_receive_skb_one_core+0x67/0x90\n ? process_backlog+0x97/0x2c0\n __netif_receive_skb+0x22/0x80",
      "affected": [
        {
          "vendor": "Linux",
          "product": "Linux",
          "defaultStatus": "unaffected",
          "versions": [
            {
              "version": "7eef18c0479ba5d9f54fba30cd77c233ebca3eb1",
              "status": "affected",
              "versionType": "git",
              "lessThan": "6950df42a03c9ac9290503ced3f371199cb68fa9"
            },
            {
              "version": "55dd22c5d029423f513fd849e633adf0e9c10d0c",
              "status": "affected",
              "versionType": "git",
              "lessThan": "b6d44072117bba057d50f7a2f96e5d070c65926d"
            },
            {
              "version": "0c71437dd50dd687c15d8ca80b3b68f10bb21d63",
              "status": "affected",
              "versionType": "git",
              "lessThan": "9ab896775f98ff54b68512f345eed178bf961084"
            },
            {
              "version": "0c71437dd50dd687c15d8ca80b3b68f10bb21d63",
              "status": "affected",
              "versionType": "git",
              "lessThan": "1740a1e45eee65099a92fb502e1e67e63aad277d"
            },
            {
              "version": "0c71437dd50dd687c15d8ca80b3b68f10bb21d63",
              "status": "affected",
              "versionType": "git",
              "lessThan": "d0553680f94c49bbe0e39eb50d033ba563b4212d"
            },
            {
              "version": "5e1fc537c1be332aef9621ca9146aeb3ba59522f",
              "status": "affected",
              "versionType": "git"
            },
            {
              "version": "5.4.138",
              "status": "affected",
              "versionType": "semver",
              "lessThan": "5.4.232"
            },
            {
              "version": "5.10.56",
              "status": "affected",
              "versionType": "semver",
              "lessThan": "5.10.168"
            },
            {
              "version": "5.13.8",
              "status": "affected",
              "versionType": "semver",
              "lessThan": "5.14"
            }
          ]
        },
        {
          "vendor": "Linux",
          "product": "Linux",
          "defaultStatus": "affected",
          "versions": [
            {
              "version": "5.14",
              "status": "affected"
            },
            {
              "version": "0",
              "status": "unaffected",
              "versionType": "semver",
              "lessThan": "5.14"
            },
            {
              "version": "5.4.232",
              "status": "unaffected",
              "versionType": "semver",
              "lessThanOrEqual": "5.4.*"
            },
            {
              "version": "5.10.168",
              "status": "unaffected",
              "versionType": "semver",
              "lessThanOrEqual": "5.10.*"
            },
            {
              "version": "5.15.93",
              "status": "unaffected",
              "versionType": "semver",
              "lessThanOrEqual": "5.15.*"
            },
            {
              "version": "6.1.11",
              "status": "unaffected",
              "versionType": "semver",
              "lessThanOrEqual": "6.1.*"
            },
            {
              "version": "6.2",
              "status": "unaffected",
              "versionType": "original_commit_for_fix",
              "lessThanOrEqual": "*"
            }
          ]
        }
      ]
    }
  }
}