{"cve":"CVE-2021-4454","nvd":{"published":"2025-03-27T17:15:35.820","modified":"2026-10-15T22:17:22.303","status":"Modified","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","cvss_v4":null,"cvss_v3":{"version":"3.1","vector":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H","score":5.5},"cwes":[],"references":["https://git.kernel.org/stable/c/1740a1e45eee65099a92fb502e1e67e63aad277d","https://git.kernel.org/stable/c/6950df42a03c9ac9290503ced3f371199cb68fa9","https://git.kernel.org/stable/c/9ab896775f98ff54b68512f345eed178bf961084","https://git.kernel.org/stable/c/b6d44072117bba057d50f7a2f96e5d070c65926d","https://git.kernel.org/stable/c/d0553680f94c49bbe0e39eb50d033ba563b4212d"],"products":["linux:linux_kernel"],"source":"nvd","synced_at":"2026-10-19T22:00:28.034033815+00:00"},"epss":{"cve":"CVE-2021-4454","score":0.00591,"percentile":0.4795,"date":"2026-10-25"},"kev":null,"osv":[],"attribution":["This product uses the NVD API but is not endorsed or certified by the NVD.","EPSS scores: FIRST Exploit Prediction Scoring System, https://www.first.org/epss","Known exploited vulnerabilities: CISA Known Exploited Vulnerabilities Catalog, https://www.cisa.gov/known-exploited-vulnerabilities-catalog","Package advisories: OSV (https://osv.dev), from the GitHub Advisory Database, PyPA, Go, RustSec and other ecosystem databases, under CC-BY 4.0 or CC0","CVE records: the CVE Program's CVE List (https://www.cve.org), under its terms of use (https://www.cve.org/Legal/TermsOfUse). CVE is a registered trademark of The MITRE Corporation; this product is not affiliated with the CVE Program."]}