{"id":"CVE-2021-4454","state":"PUBLISHED","title":"can: j1939: fix errant WARN_ON_ONCE in j1939_session_deactivate","description":"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","publishedAt":"2025-03-27T16:37:09.381Z","updatedAt":"2026-10-15T21:21:06.266Z","severity":{"score":7.5,"label":"High","version":"3.1","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H","source":"Linux"},"assigner":"Linux","products":["Linux Linux"],"affected":[{"vendor":"Linux","product":"Linux","defaultStatus":"unaffected","versions":[{"version":"7eef18c0479ba5d9f54fba30cd77c233ebca3eb1","status":"affected","lessThan":"6950df42a03c9ac9290503ced3f371199cb68fa9","versionType":"git"},{"version":"55dd22c5d029423f513fd849e633adf0e9c10d0c","status":"affected","lessThan":"b6d44072117bba057d50f7a2f96e5d070c65926d","versionType":"git"},{"version":"0c71437dd50dd687c15d8ca80b3b68f10bb21d63","status":"affected","lessThan":"9ab896775f98ff54b68512f345eed178bf961084","versionType":"git"},{"version":"0c71437dd50dd687c15d8ca80b3b68f10bb21d63","status":"affected","lessThan":"1740a1e45eee65099a92fb502e1e67e63aad277d","versionType":"git"},{"version":"0c71437dd50dd687c15d8ca80b3b68f10bb21d63","status":"affected","lessThan":"d0553680f94c49bbe0e39eb50d033ba563b4212d","versionType":"git"},{"version":"5e1fc537c1be332aef9621ca9146aeb3ba59522f","status":"affected","versionType":"git"},{"version":"5.4.138","status":"affected","lessThan":"5.4.232","versionType":"semver"},{"version":"5.10.56","status":"affected","lessThan":"5.10.168","versionType":"semver"},{"version":"5.13.8","status":"affected","lessThan":"5.14","versionType":"semver"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["net/can/j1939/transport.c"]},{"vendor":"Linux","product":"Linux","defaultStatus":"affected","versions":[{"version":"5.14","status":"affected"},{"version":"0","status":"unaffected","lessThan":"5.14","versionType":"semver"},{"version":"5.4.232","status":"unaffected","lessThanOrEqual":"5.4.*","versionType":"semver"},{"version":"5.10.168","status":"unaffected","lessThanOrEqual":"5.10.*","versionType":"semver"},{"version":"5.15.93","status":"unaffected","lessThanOrEqual":"5.15.*","versionType":"semver"},{"version":"6.1.11","status":"unaffected","lessThanOrEqual":"6.1.*","versionType":"semver"},{"version":"6.2","status":"unaffected","lessThanOrEqual":"*","versionType":"original_commit_for_fix"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["net/can/j1939/transport.c"]}],"references":["https://git.kernel.org/stable/c/6950df42a03c9ac9290503ced3f371199cb68fa9","https://git.kernel.org/stable/c/b6d44072117bba057d50f7a2f96e5d070c65926d","https://git.kernel.org/stable/c/9ab896775f98ff54b68512f345eed178bf961084","https://git.kernel.org/stable/c/1740a1e45eee65099a92fb502e1e67e63aad277d","https://git.kernel.org/stable/c/d0553680f94c49bbe0e39eb50d033ba563b4212d"],"weaknesses":[],"ingestedAt":"2026-10-29T19:49:23.890Z","source":{"repository":"CVEProject/cvelistV5","path":"cves/2021/4xxx/CVE-2021-4454.json","commit":"556c9d3a8cd17e218bb8e452ba7cd619a384ff47"},"raw":{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2021-4454","state":"PUBLISHED","datePublished":"2025-03-27T16:37:09.381Z","dateUpdated":"2026-10-15T21:21:06.266Z","assignerShortName":"Linux","assignerOrgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","dateReserved":"2025-02-26T02:29:43.631Z"},"containers":{"cna":{"title":"can: j1939: fix errant WARN_ON_ONCE in j1939_session_deactivate","descriptions":[{"lang":"en","value":"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","lessThan":"6950df42a03c9ac9290503ced3f371199cb68fa9","versionType":"git"},{"version":"55dd22c5d029423f513fd849e633adf0e9c10d0c","status":"affected","lessThan":"b6d44072117bba057d50f7a2f96e5d070c65926d","versionType":"git"},{"version":"0c71437dd50dd687c15d8ca80b3b68f10bb21d63","status":"affected","lessThan":"9ab896775f98ff54b68512f345eed178bf961084","versionType":"git"},{"version":"0c71437dd50dd687c15d8ca80b3b68f10bb21d63","status":"affected","lessThan":"1740a1e45eee65099a92fb502e1e67e63aad277d","versionType":"git"},{"version":"0c71437dd50dd687c15d8ca80b3b68f10bb21d63","status":"affected","lessThan":"d0553680f94c49bbe0e39eb50d033ba563b4212d","versionType":"git"},{"version":"5e1fc537c1be332aef9621ca9146aeb3ba59522f","status":"affected","versionType":"git"},{"version":"5.4.138","status":"affected","lessThan":"5.4.232","versionType":"semver"},{"version":"5.10.56","status":"affected","lessThan":"5.10.168","versionType":"semver"},{"version":"5.13.8","status":"affected","lessThan":"5.14","versionType":"semver"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["net/can/j1939/transport.c"]},{"vendor":"Linux","product":"Linux","defaultStatus":"affected","versions":[{"version":"5.14","status":"affected"},{"version":"0","status":"unaffected","lessThan":"5.14","versionType":"semver"},{"version":"5.4.232","status":"unaffected","lessThanOrEqual":"5.4.*","versionType":"semver"},{"version":"5.10.168","status":"unaffected","lessThanOrEqual":"5.10.*","versionType":"semver"},{"version":"5.15.93","status":"unaffected","lessThanOrEqual":"5.15.*","versionType":"semver"},{"version":"6.1.11","status":"unaffected","lessThanOrEqual":"6.1.*","versionType":"semver"},{"version":"6.2","status":"unaffected","lessThanOrEqual":"*","versionType":"original_commit_for_fix"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["net/can/j1939/transport.c"]}],"references":[{"url":"https://git.kernel.org/stable/c/6950df42a03c9ac9290503ced3f371199cb68fa9"},{"url":"https://git.kernel.org/stable/c/b6d44072117bba057d50f7a2f96e5d070c65926d"},{"url":"https://git.kernel.org/stable/c/9ab896775f98ff54b68512f345eed178bf961084"},{"url":"https://git.kernel.org/stable/c/1740a1e45eee65099a92fb502e1e67e63aad277d"},{"url":"https://git.kernel.org/stable/c/d0553680f94c49bbe0e39eb50d033ba563b4212d"}],"metrics":[{"cvssV3_1":{"version":"3.1","vectorString":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H","baseScore":7.5,"baseSeverity":"HIGH"},"scenarios":[{"lang":"en","value":"AV:N - The WARN fires on the packet receive path (can_rcv → j1939_can_recv → j1939_tp_recv → j1939_xtp_rx_eoma/abort → j1939_session_deactivate). An unauthenticated CAN/J1939 peer can trigger it without local code on the target, consistent with other packet-triggered j1939 scores (e.g. CVE-2023-52887, CVE-2026-22997).\nAC:L - The attacker controls both sides of the race by injecting concurrent TP.CM EOMA and Abort frames for the same session; packet content and timing are fully attacker-influenced, so success does not depend on external conditions.\nPR:N - J1939/CAN receive processing has no authentication or credential check; once a legitimate J1939 socket is bound (normal deployment state), an unauthenticated bus peer can inject the crafted frame sequence.\nUI:N - Frames are processed automatically in softirq receive context; no victim or administrator action is required beyond the target already running the J1939 stack.\nS:U - Impact is confined to kernel J1939 session handling within the same host kernel authority and does not cross a VM, IOMMU, or sandbox boundary.\nC:N - The defect is only a spurious WARN_ON_ONCE; the concurrent deactivate path checks session active state before putting, and investigation found no info leak, OOB read, or UAF disclosure primitive.\nI:N - No out-of-bounds write, type confusion, or other integrity/write primitive exists—the fix only removes an incorrect assertion while leaving correct deactivate_locked behavior unchanged.\nA:H - WARN_ON_ONCE in softirq receive context can panic the kernel when panic_on_warn is set (and warn_limit exhaustion similarly), producing a denial of service inducible by an unauthenticated peer."}]}],"providerMetadata":{"shortName":"Linux","orgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","dateUpdated":"2026-08-05T08:44:58.812Z"},"cpeApplicability":[{"nodes":[{"operator":"OR","negate":false,"cpeMatch":[{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.4.138","versionEndExcluding":"5.4.232"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.10.56","versionEndExcluding":"5.10.168"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.14","versionEndExcluding":"5.15.93"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.14","versionEndExcluding":"6.1.11"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.14","versionEndExcluding":"6.2"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.13.8"}]}]}],"x_generator":{"engine":"bippy-1.2.0"}},"adp":[{"title":"CISA ADP Vulnrichment","metrics":[{"other":{"type":"ssvc","content":{"id":"CVE-2021-4454","role":"CISA Coordinator","options":[{"Exploitation":"none"},{"Automatable":"yes"},{"Technical Impact":"partial"}],"version":"2.0.3","timestamp":"2026-10-15T21:02:43.206452Z"}}}],"providerMetadata":{"shortName":"CISA-ADP","orgId":"134c704f-9b21-4f2e-91b3-4a467353bcc0","dateUpdated":"2026-10-15T21:21:06.266Z"}}]}}}