{ "dataType": "CVE_RECORD", "dataVersion": "5.2", "cveMetadata": { "cveId": "CVE-2026-72123", "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "state": "PUBLISHED", "assignerShortName": "Linux", "dateReserved": "2026-08-09T03:40:39.907Z", "datePublished": "2026-08-15T05:53:01.433Z", "dateUpdated": "2026-08-19T16:36:18.988Z" }, "containers": { "cna": { "providerMetadata": { "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "shortName": "Linux", "dateUpdated": "2026-08-19T16:36:18.988Z" }, "descriptions": [ { "lang": "en", "value": "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." } ], "metrics": [ { "cvssV3_1": { "version": "3.1", "vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H", "baseScore": 7.8, "baseSeverity": "HIGH" }, "scenarios": [ { "lang": "en", "value": "AV:L - Exploitation requires local BCM socket syscalls (sendmsg with RX_SETUP/SETTIMER/ival2 throttling and RX_DELETE); CAN frames can be injected locally via loopback without physical bus access.\nAC:L - The attacker controls both sides of the race by concurrently issuing RX_DELETE teardown and delivering matching CAN frames (e.g., via threads or paired BCM/RAW sockets), making the thrtimer re-arm UAF reliably triggerable.\nPR:L - No kernel capability check gates AF_CAN/CAN_BCM socket creation or bcm_sendmsg opcodes; any unprivileged local user with socket access (including via user namespaces with vcan) can reach the vulnerable path.\nUI:N - No victim interaction is required; the attacker self-triggers the race through their own BCM socket operations and locally injected CAN traffic.\nS:U - Impact is confined to kernel memory corruption and local privilege escalation within the same kernel security boundary, not a cross-boundary escape such as VM or IOMMU bypass.\nC:H - The thrtimer UAF dereferences freed bcm_op fields (locks, frame buffers, op->sk) in bcm_rx_thr_handler/bcm_send_to_user, enabling attacker-controlled heap reuse and arbitrary kernel memory disclosure.\nI:H - UAF on the bcm_op slab object allows heap spraying to corrupt function pointers, timers, and sock structures, providing a standard path to arbitrary kernel writes and local privilege escalation.\nA:H - The freed-op dereference in the hrtimer softirq path causes kernel oops/panic under normal exploitation attempts, and successful memory corruption can crash or hang the system." } ] } ], "affected": [ { "product": "Linux", "vendor": "Linux", "defaultStatus": "unaffected", "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "programFiles": [ "net/can/bcm.c" ], "versions": [ { "version": "85cd41070df992d3c0dfd828866fdd243d3b774a", "lessThan": "de5fce46637de05bef56ec08528127676eb6fc9b", "status": "affected", "versionType": "git" }, { "version": "f34f2a18e47b73e48f90a757e1f4aaa8c7d665a1", "lessThan": "036a8c320ca11bc912e8027adcfad14b326f067e", "status": "affected", "versionType": "git" }, { "version": "f1b4e32aca0811aa011c76e5d6cf2fa19224b386", "lessThan": "3cf4fd5316f449811d8baf1bc6978ef5a7b743a9", "status": "affected", "versionType": "git" }, { "version": "f1b4e32aca0811aa011c76e5d6cf2fa19224b386", "lessThan": "4177762f70646ac48a2af382e45a795cbd295198", "status": "affected", "versionType": "git" }, { "version": "f1b4e32aca0811aa011c76e5d6cf2fa19224b386", "lessThan": "6fd08e8d826c3aa4cc7021f5f9cdbb7fa7441d3f", "status": "affected", "versionType": "git" }, { "version": "f1b4e32aca0811aa011c76e5d6cf2fa19224b386", "lessThan": "cd830e0bc25ee2d38cbfbdbb3cd77c5f53b2b6d5", "status": "affected", "versionType": "git" }, { "version": "f1b4e32aca0811aa011c76e5d6cf2fa19224b386", "lessThan": "ce2d4b121fb7545e1ed588e860c8e5fd5ad45224", "status": "affected", "versionType": "git" }, { "version": "f1b4e32aca0811aa011c76e5d6cf2fa19224b386", "lessThan": "68973f9db76144825e4f35dfdc80fb8279eb2d57", "status": "affected", "versionType": "git" }, { "version": "fbac09a3b8890003c0c55294c00709f3ae5501bb", "status": "affected", "versionType": "git" }, { "version": "5b48f5711f1c630841ab78dcc061de902f0e37bf", "status": "affected", "versionType": "git" }, { "version": "edb4baffb9483141a50fb7f7146cfe4a4c0c2db8", "status": "affected", "versionType": "git" }, { "version": "5.10.130", "lessThan": "5.10.265", "status": "affected", "versionType": "semver" }, { "version": "5.15.54", "lessThan": "5.15.216", "status": "affected", "versionType": "semver" }, { "version": "4.19.252", "lessThan": "4.20", "status": "affected", "versionType": "semver" }, { "version": "5.4.205", "lessThan": "5.5", "status": "affected", "versionType": "semver" }, { "version": "5.18.11", "lessThan": "5.19", "status": "affected", "versionType": "semver" } ] }, { "product": "Linux", "vendor": "Linux", "defaultStatus": "affected", "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "programFiles": [ "net/can/bcm.c" ], "versions": [ { "version": "5.19", "status": "affected" }, { "version": "0", "lessThan": "5.19", "status": "unaffected", "versionType": "semver" }, { "version": "5.10.265", "lessThanOrEqual": "5.10.*", "status": "unaffected", "versionType": "semver" }, { "version": "5.15.216", "lessThanOrEqual": "5.15.*", "status": "unaffected", "versionType": "semver" }, { "version": "6.1.178", "lessThanOrEqual": "6.1.*", "status": "unaffected", "versionType": "semver" }, { "version": "6.6.145", "lessThanOrEqual": "6.6.*", "status": "unaffected", "versionType": "semver" }, { "version": "6.12.97", "lessThanOrEqual": "6.12.*", "status": "unaffected", "versionType": "semver" }, { "version": "6.18.40", "lessThanOrEqual": "6.18.*", "status": "unaffected", "versionType": "semver" }, { "version": "7.1.5", "lessThanOrEqual": "7.1.*", "status": "unaffected", "versionType": "semver" }, { "version": "7.2", "lessThanOrEqual": "*", "status": "unaffected", "versionType": "original_commit_for_fix" } ] } ], "cpeApplicability": [ { "nodes": [ { "operator": "OR", "negate": false, "cpeMatch": [ { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "5.10.130", "versionEndExcluding": "5.10.265" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "5.15.54", "versionEndExcluding": "5.15.216" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "5.19", "versionEndExcluding": "6.1.178" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "5.19", "versionEndExcluding": "6.6.145" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "5.19", "versionEndExcluding": "6.12.97" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "5.19", "versionEndExcluding": "6.18.40" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "5.19", "versionEndExcluding": "7.1.5" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "5.19", "versionEndExcluding": "7.2" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "4.19.252" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "5.4.205" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "5.18.11" } ] } ] } ], "references": [ { "url": "https://git.kernel.org/stable/c/de5fce46637de05bef56ec08528127676eb6fc9b" }, { "url": "https://git.kernel.org/stable/c/036a8c320ca11bc912e8027adcfad14b326f067e" }, { "url": "https://git.kernel.org/stable/c/3cf4fd5316f449811d8baf1bc6978ef5a7b743a9" }, { "url": "https://git.kernel.org/stable/c/4177762f70646ac48a2af382e45a795cbd295198" }, { "url": "https://git.kernel.org/stable/c/6fd08e8d826c3aa4cc7021f5f9cdbb7fa7441d3f" }, { "url": "https://git.kernel.org/stable/c/cd830e0bc25ee2d38cbfbdbb3cd77c5f53b2b6d5" }, { "url": "https://git.kernel.org/stable/c/ce2d4b121fb7545e1ed588e860c8e5fd5ad45224" }, { "url": "https://git.kernel.org/stable/c/68973f9db76144825e4f35dfdc80fb8279eb2d57" } ], "title": "can: bcm: defer rx_op deallocation to workqueue to fix thrtimer UAF", "x_generator": { "engine": "bippy-1.2.0" } } } }