{"apiVersion":"1.0","identifier":"CVE-2026-72123","description":"In the Linux kernel, the following vulnerability has been resolved: can: bcm: defer rx_op deallocation to workqueue to fix thrtimer UAF Commit f1b4e32aca08 (-can: bcm: use call_rcu() instead of costly synchronize_rcu()-) replaced synchronize_rcu() in bcm_delete_rx_op() with call_rcu() and introduced the RX_NO_AUTOTIMER flag. However, this flag check was omitted for thrtimer in the packet rx fast-path. During BCM RX operation teardown, a concurrent RCU reader (bcm_rx_handler) can race and re-arm thrtimer via bcm_rx_update_and_send() after call_rcu() has been scheduled. Once the RCU grace period elapses, bcm_op is freed. The subsequently firing thrtimer then dereferences the deallocated op, causing a UAF. Adding flag checks to the rx fast-path (bcm_rx_update_and_send) does not fully close the TOCTOU race and introduces latency for every CAN frame. Conversely, calling hrtimer_cancel() directly inside the RCU callback (softirq context) is fatal as hrtimer_cancel() can sleep, triggering a -scheduling while atomic- panic. Resolve this by deferring the timer cancellation and memory free to a dedicated unbound workqueue (bcm_wq). The RCU callback now queues a work item to bcm_wq, which safely cancels both timers and deallocates memory in sleepable process context. A dedicated workqueue is used to prevent system-wide WQ saturation and is cleanly flushed/destroyed on module unload to avoid rmmod page faults. Since the deferred work can now outlive the calling context by an unbounded amount, also take a reference on op->sk when it is assigned and drop it only once the deferred work has cancelled both timers, so a socket can no longer be freed out from under a still-armed timer whose callback (bcm_send_to_user()) dereferences op->sk.","publishedAt":"2026-08-15T06:21:29","lastModifiedAt":"2026-08-19T17:20:59","sourceUrl":"https://nvd.nist.gov/vuln/detail/CVE-2026-72123","cvssScore":7.8,"cvssVector":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H","epssProbability":0.00164,"riskScore":0.79,"affectedProduct":"Linux kernel","affectedVersions":"unknown","vulnerabilityType":"Kernel","operatingSystems":[],"links":{"self":"https://www.redsauce.net/api/cves/CVE-2026-72123","webPages":{"es":"https://www.redsauce.net/es/cves/CVE-2026-72123","en":"https://www.redsauce.net/en/cves/CVE-2026-72123","fr":"https://www.redsauce.net/fr/cves/CVE-2026-72123","pt":"https://www.redsauce.net/pt/cves/CVE-2026-72123","de":"https://www.redsauce.net/de/cves/CVE-2026-72123","sk":"https://www.redsauce.net/sk/cves/CVE-2026-72123","el":"https://www.redsauce.net/el/cves/CVE-2026-72123"},"source":"https://nvd.nist.gov/vuln/detail/CVE-2026-72123"}}