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CVE-2026-72123— can: bcm: defer rx_op deallocation to workqueue to fix thrtimer UAF

Quick assessment

Affected
Linux Linux
Exploitation
No confirmed in-the-wild exploitation; assess based on exposure
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

Linux kernel是美国Linux基金会开源的一个操作系统内核。 Linux kernel 5.19版本存在安全漏洞，该漏洞源于can:bcm模块对thrtimer处理不当，在RX操作拆除期间并发RCU读取器可重新启动thrtimer，导致释放后重用，可能造成内核崩溃或拒绝服务。

CVSS 7.8 · High EPSS 0.16% · P6

Possible ATT&CK Techniques 1 AI

T1068 · Exploitation for Privilege Escalation

Affected Version Matrix 26

VendorProduct Version RangeStatus
Linux Linux 85cd41070df992d3c0dfd828866fdd243d3b774a< de5fce46637de05bef56ec08528127676eb6fc9b affected
f34f2a18e47b73e48f90a757e1f4aaa8c7d665a1< 036a8c320ca11bc912e8027adcfad14b326f067e affected
f1b4e32aca0811aa011c76e5d6cf2fa19224b386< 3cf4fd5316f449811d8baf1bc6978ef5a7b743a9 affected
f1b4e32aca0811aa011c76e5d6cf2fa19224b386< 4177762f70646ac48a2af382e45a795cbd295198 affected
f1b4e32aca0811aa011c76e5d6cf2fa19224b386< 6fd08e8d826c3aa4cc7021f5f9cdbb7fa7441d3f affected
f1b4e32aca0811aa011c76e5d6cf2fa19224b386< cd830e0bc25ee2d38cbfbdbb3cd77c5f53b2b6d5 affected
f1b4e32aca0811aa011c76e5d6cf2fa19224b386< ce2d4b121fb7545e1ed588e860c8e5fd5ad45224 affected
f1b4e32aca0811aa011c76e5d6cf2fa19224b386< 68973f9db76144825e4f35dfdc80fb8279eb2d57 affected
… +18 more rows
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I. Basic Information for CVE-2026-72123

Vulnerability Information
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Vulnerability Title
can: bcm: defer rx_op deallocation to workqueue to fix thrtimer UAF
Source: CVE Program / CVE List V5
Vulnerability 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.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
Source: CVE Program / CVE List V5
Vulnerability Type
N/A
Source: CVE Program / CVE List V5
Vulnerability Title
Linux kernel 安全漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
Linux kernel是美国Linux基金会开源的一个操作系统内核。 Linux kernel 5.19版本存在安全漏洞，该漏洞源于can:bcm模块对thrtimer处理不当，在RX操作拆除期间并发RCU读取器可重新启动thrtimer，导致释放后重用，可能造成内核崩溃或拒绝服务。
Source: CNNVD (China National Vulnerability Database)
CVSS Information
N/A
Source: CNNVD (China National Vulnerability Database)
Vulnerability Type
N/A
Source: CNNVD (China National Vulnerability Database)

Affected Products

Vendor Product Affected Versions CPE Subscribe
Linux Linux 85cd41070df992d3c0dfd828866fdd243d3b774a ~ de5fce46637de05bef56ec08528127676eb6fc9b -
Linux Linux 5.19 -

II. Public POCs for CVE-2026-72123

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III. Intelligence Information for CVE-2026-72123

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Patches & Fixes for CVE-2026-72123 (7)

Same Patch Batch · Linux · 2026-08-15 · 845 CVEs total

CVE-2026-74475 10.0 CRITICAL vxlan: use neigh_ha_snapshot() in route_shortcircuit()
CVE-2026-74280 10.0 CRITICAL crypto: marvell/octeontx - fix DMA cleanup using wrong loop index
CVE-2026-72407 10.0 CRITICAL geneve: validate inner network offset in geneve_gro_complete()
CVE-2026-72408 10.0 CRITICAL geneve: gate GRO hint in geneve_gro_complete() on gs->gro_hint
CVE-2026-72421 10.0 CRITICAL ipv4: fib: Don't ignore error route in local/main tables.
CVE-2026-74309 10.0 CRITICAL vdpa/octeon_ep: fix IRQ-to-ring mapping in interrupt handler
CVE-2026-74279 10.0 CRITICAL crypto: cavium/cpt - fix DMA cleanup using wrong loop index
CVE-2026-72493 9.9 CRITICAL net: serialize netif_running() check in enqueue_to_backlog()
CVE-2026-72381 9.8 CRITICAL ksmbd: fix use-after-free of fp->owner.name in durable handle owner check
CVE-2026-72393 9.8 CRITICAL eth: fbnic: don't cache shinfo across skb realloc
CVE-2026-74401 9.8 CRITICAL dlm: fix add msg handle in send_queue ordered
CVE-2026-74406 9.8 CRITICAL vxlan: Fix potential null-ptr-deref in vxlan_gro_prepare_receive().
CVE-2026-72355 9.8 CRITICAL netfs: Fix barriering when walking subrequest list
CVE-2026-72339 9.8 CRITICAL qede: fix off-by-one in BD ring consumption on build_skb failure
CVE-2026-72211 9.8 CRITICAL ntfs: grow index root value before reparent header update
CVE-2026-72194 9.8 CRITICAL fs/ntfs3: add depth limit to indx_find_buffer to prevent stack overflow
CVE-2026-72351 9.8 CRITICAL gue: validate REMCSUM private option length
CVE-2026-72366 9.8 CRITICAL netfs: Fix netfs_create_write_req() to handle async cache object creation
CVE-2026-72098 9.8 CRITICAL dm-verity: fix buffer overflow in FEC calculation
CVE-2026-72083 9.8 CRITICAL scsi: target: core: Fix iSCSI ISID use-after-free in REGISTER AND MOVE

Showing top 20 of 845 CVEs. View all on vendor page &rarr; →

IV. Related Vulnerabilities

Same product: Linux
Same vendor: Linux

V. Comments for CVE-2026-72123

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