{"id":"CVE-2026-72123","revision":"9c472e70e4c64efcb434d3dafecd1eaf","records":[{"revision":"9c472e70e4c64efcb434d3dafecd1eaf","observedAt":"2026-10-23T15:48:27.903+00:00","statement":{"source":"cve-program","id":"CVE-2026-72123","aliases":[],"title":"can: bcm: defer rx_op deallocation to workqueue to fix thrtimer UAF","description":"In the Linux kernel, the following vulnerability has been resolved:\n\ncan: bcm: defer rx_op deallocation to workqueue to fix thrtimer UAF\n\nCommit f1b4e32aca08 (\"can: bcm: use call_rcu() instead of costly\nsynchronize_rcu()\") replaced synchronize_rcu() in bcm_delete_rx_op()\nwith call_rcu() and introduced the RX_NO_AUTOTIMER flag.\n\nHowever, this flag check was omitted for thrtimer in the packet rx\nfast-path. During BCM RX operation teardown, a concurrent RCU reader\n(bcm_rx_handler) can race and re-arm thrtimer via\nbcm_rx_update_and_send() after call_rcu() has been scheduled.  Once\nthe RCU grace period elapses, bcm_op is freed.  The subsequently\nfiring thrtimer then dereferences the deallocated op, causing a UAF.\n\nAdding flag checks to the rx fast-path (bcm_rx_update_and_send) does not\nfully close the TOCTOU race and introduces latency for every CAN frame.\nConversely, calling hrtimer_cancel() directly inside the RCU callback\n(softirq context) is fatal as hrtimer_cancel() can sleep, triggering\na \"scheduling while atomic\" panic.\n\nResolve this by deferring the timer cancellation and memory free to a\ndedicated unbound workqueue (bcm_wq).  The RCU callback now queues a\nwork item to bcm_wq, which safely cancels both timers and deallocates\nmemory in sleepable process context.  A dedicated workqueue is used to\nprevent system-wide WQ saturation and is cleanly flushed/destroyed\non module unload to avoid rmmod page faults.\n\nSince the deferred work can now outlive the calling context by an\nunbounded amount, also take a reference on op->sk when it is assigned\nand drop it only once the deferred work has cancelled both timers, so a\nsocket can no longer be freed out from under a still-armed timer whose\ncallback (bcm_send_to_user()) dereferences op->sk.","state":0,"publishedAt":"2026-08-15T05:53:01.433+00:00","modifiedAt":"2026-10-16T18:44:57.598+00:00","affected":[{"ecosystem":"Vendor product","name":"Linux","ranges":[],"versions":[],"rawVersionEvidence":"{\n                    \"product\": \"Linux\",\n                    \"vendor\": \"Linux\",\n                    \"defaultStatus\": \"unaffected\",\n                    \"repo\": \"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git\",\n                    \"programFiles\": [\n                        \"net/can/bcm.c\"\n                    ],\n                    \"versions\": [\n                        {\n                            \"version\": \"85cd41070df992d3c0dfd828866fdd243d3b774a\",\n                            \"lessThan\": \"de5fce46637de05bef56ec08528127676eb6fc9b\",\n                            \"status\": \"affected\",\n                            \"versionType\": \"git\"\n                        },\n                        {\n                            \"version\": \"f34f2a18e47b73e48f90a757e1f4aaa8c7d665a1\",\n                            \"lessThan\": \"036a8c320ca11bc912e8027adcfad14b326f067e\",\n                            \"status\": \"affected\",\n                            \"versionType\": \"git\"\n                        },\n                        {\n                            \"version\": \"f1b4e32aca0811aa011c76e5d6cf2fa19224b386\",\n                            \"lessThan\": \"3cf4fd5316f449811d8baf1bc6978ef5a7b743a9\",\n                            \"status\": \"affected\",\n                            \"versionType\": \"git\"\n                        },\n                        {\n                            \"version\": \"f1b4e32aca0811aa011c76e5d6cf2fa19224b386\",\n                            \"lessThan\": \"4177762f70646ac48a2af382e45a795cbd295198\",\n                            \"status\": \"affected\",\n                            \"versionType\": \"git\"\n                        },\n                        {\n                            \"version\": \"f1b4e32aca0811aa011c76e5d6cf2fa19224b386\",\n                            \"lessThan\": \"6fd08e8d826c3aa4cc7021f5f9cdbb7fa7441d3f\",\n                            \"status\": \"affected\",\n                            \"versionType\": \"git\"\n                        },\n                        {\n                            \"version\": \"f1b4e32aca0811aa011c76e5d6cf2fa19224b386\",\n                            \"lessThan\": \"cd830e0bc25ee2d38cbfbdbb3cd77c5f53b2b6d5\",\n                            \"status\": \"affected\",\n                            \"versionType\": \"git\"\n                        },\n                        {\n                            \"version\": \"f1b4e32aca0811aa011c76e5d6cf2fa19224b386\",\n                            \"lessThan\": \"ce2d4b121fb7545e1ed588e860c8e5fd5ad45224\",\n                            \"status\": \"affected\",\n                            \"versionType\": \"git\"\n                        },\n                        {\n                            \"version\": \"f1b4e32aca0811aa011c76e5d6cf2fa19224b386\",\n                            \"lessThan\": \"68973f9db76144825e4f35dfdc80fb8279eb2d57\",\n                            \"status\": \"affected\",\n                            \"versionType\": \"git\"\n                        },\n                        {\n                            \"version\": \"fbac09a3b8890003c0c55294c00709f3ae5501bb\",\n                            \"status\": \"affected\",\n                            \"versionType\": \"git\"\n                        },\n                        {\n                            \"version\": \"5b48f5711f1c630841ab78dcc061de902f0e37bf\",\n                            \"status\": \"affected\",\n                            \"versionType\": \"git\"\n                        },\n                        {\n                            \"version\": \"edb4baffb9483141a50fb7f7146cfe4a4c0c2db8\",\n                            \"status\": \"affected\",\n                            \"versionType\": \"git\"\n                        },\n                        {\n                            \"version\": \"5.10.130\",\n                            \"lessThan\": \"5.10.265\",\n                            \"status\": \"affected\",\n                            \"versionType\": \"semver\"\n                        },\n                        {\n                            \"version\": \"5.15.54\",\n                            \"lessThan\": \"5.15.216\",\n                            \"status\": \"affected\",\n                            \"versionType\": \"semver\"\n                        },\n                        {\n                            \"version\": \"4.19.252\",\n                            \"lessThan\": \"4.20\",\n                            \"status\": \"affected\",\n                            \"versionType\": \"semver\"\n                        },\n                        {\n                            \"version\": \"5.4.205\",\n                            \"lessThan\": \"5.5\",\n                            \"status\": \"affected\",\n                            \"versionType\": \"semver\"\n                        },\n                        {\n                            \"version\": \"5.18.11\",\n                            \"lessThan\": \"5.19\",\n                            \"status\": \"affected\",\n                            \"versionType\": \"semver\"\n                        }\n                    ]\n                }"},{"ecosystem":"Vendor product","name":"Linux","ranges":[],"versions":[],"rawVersionEvidence":"{\n                    \"product\": \"Linux\",\n                    \"vendor\": \"Linux\",\n                    \"defaultStatus\": \"affected\",\n                    \"repo\": \"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git\",\n                    \"programFiles\": [\n                        \"net/can/bcm.c\"\n                    ],\n                    \"versions\": [\n                        {\n                            \"version\": \"5.19\",\n                            \"status\": \"affected\"\n                        },\n                        {\n                            \"version\": \"0\",\n                            \"lessThan\": \"5.19\",\n                            \"status\": \"unaffected\",\n                            \"versionType\": \"semver\"\n                        },\n                        {\n                            \"version\": \"5.10.265\",\n                            \"lessThanOrEqual\": \"5.10.*\",\n                            \"status\": \"unaffected\",\n                            \"versionType\": \"semver\"\n                        },\n                        {\n                            \"version\": \"5.15.216\",\n                            \"lessThanOrEqual\": \"5.15.*\",\n                            \"status\": \"unaffected\",\n                            \"versionType\": \"semver\"\n                        },\n                        {\n                            \"version\": \"6.1.178\",\n                            \"lessThanOrEqual\": \"6.1.*\",\n                            \"status\": \"unaffected\",\n                            \"versionType\": \"semver\"\n                        },\n                        {\n                            \"version\": \"6.6.145\",\n                            \"lessThanOrEqual\": \"6.6.*\",\n                            \"status\": \"unaffected\",\n                            \"versionType\": \"semver\"\n                        },\n                        {\n                            \"version\": \"6.12.97\",\n                            \"lessThanOrEqual\": \"6.12.*\",\n                            \"status\": \"unaffected\",\n                            \"versionType\": \"semver\"\n                        },\n                        {\n                            \"version\": \"6.18.40\",\n                            \"lessThanOrEqual\": \"6.18.*\",\n                            \"status\": \"unaffected\",\n                            \"versionType\": \"semver\"\n                        },\n                        {\n                            \"version\": \"7.1.5\",\n                            \"lessThanOrEqual\": \"7.1.*\",\n                            \"status\": \"unaffected\",\n                            \"versionType\": \"semver\"\n                        },\n                        {\n                            \"version\": \"7.2\",\n                            \"lessThanOrEqual\": \"*\",\n                            \"status\": \"unaffected\",\n                            \"versionType\": \"original_commit_for_fix\"\n                        }\n                    ]\n                }"}],"metrics":[{"system":"CVSS 3.1","vector":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H","score":7.8,"severity":"HIGH"}],"references":["https://git.kernel.org/stable/c/de5fce46637de05bef56ec08528127676eb6fc9b","https://git.kernel.org/stable/c/036a8c320ca11bc912e8027adcfad14b326f067e","https://git.kernel.org/stable/c/3cf4fd5316f449811d8baf1bc6978ef5a7b743a9","https://git.kernel.org/stable/c/4177762f70646ac48a2af382e45a795cbd295198","https://git.kernel.org/stable/c/6fd08e8d826c3aa4cc7021f5f9cdbb7fa7441d3f","https://git.kernel.org/stable/c/cd830e0bc25ee2d38cbfbdbb3cd77c5f53b2b6d5","https://git.kernel.org/stable/c/ce2d4b121fb7545e1ed588e860c8e5fd5ad45224","https://git.kernel.org/stable/c/68973f9db76144825e4f35dfdc80fb8279eb2d57"],"sourceUrl":"https://www.cve.org/CVERecord?id=CVE-2026-72123","license":"CVE Program Terms of Use","key":"cve-program:CVE-2026-72123","identifiers":["CVE-2026-72123"]},"retained":false,"historicalAffected":[]}],"coverage":[]}