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TI-2026-50403 Aliases CVE-2026-72123GHSA-8862-mgcq-cgrw

can: bcm: defer rx_op deallocation to workqueue to fix thrtimer UAF

Priority LOW 35Published · Updated

Key facts

Attack vector
Local
Privileges required
Low
User interaction
None
Attack complexity
Low
Impact type
—
Confidentiality · integrity · availability
High · High · High
Fix status
Partial Red Hat: 15 fixed, 3 without a fix

Attack profile from CVSS 3.1 · CNA. Fix status from CNA and Red Hat.

Summary

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.

Why it matters now

Exploitation None reported CISA SSVC · not in CISA KEV
EPSS 0.00169 6th percentileScored 2026-11-07
Fix Partial Linux (Linux): 5.10.265, 5.15.216, 4.20 +8Red Hat: 3 advisoriesRed Hat: 15 fixed, 3 without a fix

SSVC decision points

CISA ADP · SSVC 2.0.3

Exploitation
None
Automatable
No
Technical impact
Total

The decision (Track, Attend, Act) also depends on your mission and well-being impact; see CISA's SSVC guide.

Affected products

VendorProductAffected versionsFixed inStatusSource
LinuxLinux5.10.130 to before 5.10.265; 5.15.54 to before 5.15.216; 4.19.252 to before 4.20; 5.4.205 to before 5.5; 5.18.11 to before 5.195.10.265, 5.15.216, 4.20, 5.5, 5.19Patch availableCNA
LinuxLinux5.19 and later5.10.265, 5.15.216, 6.1.178, 6.6.145, 6.12.97, 6.18.40, 7.1.5, 7.2Patch availableCNA
  • Linux VendorLinux Affected 5.10.130 to before 5.10.265; 5.15.54 to before 5.15.216; 4.19.252 to before 4.20; 5.4.205 to before 5.5; 5.18.11 to before 5.19 Fixed in 5.10.265, 5.15.216, 4.20, 5.5, 5.19 Patch available CNA
  • Linux VendorLinux Affected 5.19 and later Fixed in 5.10.265, 5.15.216, 6.1.178, 6.6.145, 6.12.97, 6.18.40, 7.1.5, 7.2 Patch available CNA

CPE names Threatist (inferred) · 1

Inferred from how NVD named this product before; not given by a source.

CPEVersionsRoleVendor
cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*——Linux
  • cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:* Versions — — ·Linux

Remediation

  • Fix · CNA Linux (Linux) Fixed in 5.10.265, 5.15.216, 4.20, 5.5, 5.19
  • Fix · CNA Linux (Linux) Fixed in 5.10.265, 5.15.216, 6.1.178, 6.6.145, 6.12.97, 6.18.40, 7.1.5, 7.2

Red Hat 3 advisories

  • RHSA-2026:44694 Released 2026-07-23 · Red Hat rating Important
    kernel security, bug fix, and enhancement update
    • Red Hat Enterprise Linux AppStream EUS (v. 10.0) kernel-64k-debug-devel-6.12.0-55.92.1.el10_0, kernel-64k-debug-devel-matched-6.12.0-55.92.1.el10_0, kernel-64k-devel-6.12.0-55.92.1.el10_0 +12
    • Red Hat Enterprise Linux BaseOS EUS (v. 10.0) kernel-6.12.0-55.92.1.el10_0, kernel-64k-6.12.0-55.92.1.el10_0, kernel-64k-core-6.12.0-55.92.1.el10_0 +28
    • Red Hat Enterprise Linux CodeReady Linux Builder EUS (v. 10.0) kernel-tools-libs-devel-6.12.0-55.92.1.el10_0, libperf-6.12.0-55.92.1.el10_0
    • Red Hat Enterprise Linux Real Time EUS (v. 10.0) kernel-rt-6.12.0-55.92.1.el10_0, kernel-rt-64k-6.12.0-55.92.1.el10_0, kernel-rt-64k-core-6.12.0-55.92.1.el10_0 +21
    • Red Hat Enterprise Linux Real Time for NFV EUS (v. 10.0) kernel-rt-6.12.0-55.92.1.el10_0, kernel-rt-core-6.12.0-55.92.1.el10_0, kernel-rt-debug-6.12.0-55.92.1.el10_0 +11
  • RHSA-2026:43307 Released 2026-07-22 · Red Hat rating Important
    kernel security, bug fix, and enhancement update
    • Red Hat Enterprise Linux AppStream (v. 9) kernel-64k-debug-devel-5.14.0-687.29.1.el9_8, kernel-64k-debug-devel-matched-5.14.0-687.29.1.el9_8, kernel-64k-devel-5.14.0-687.29.1.el9_8 +12
    • Red Hat Enterprise Linux BaseOS (v. 9) kernel-5.14.0-687.29.1.el9_8, kernel-64k-5.14.0-687.29.1.el9_8, kernel-64k-core-5.14.0-687.29.1.el9_8 +28
    • Red Hat Enterprise Linux CodeReady Linux Builder (v. 9) kernel-tools-libs-devel-5.14.0-687.29.1.el9_8, libperf-5.14.0-687.29.1.el9_8
    • Red Hat Enterprise Linux Real Time (v. 9) kernel-rt-5.14.0-687.29.1.el9_8, kernel-rt-64k-5.14.0-687.29.1.el9_8, kernel-rt-64k-core-5.14.0-687.29.1.el9_8 +21
    • Red Hat Enterprise Linux Real Time for NFV (v. 9) kernel-rt-5.14.0-687.29.1.el9_8, kernel-rt-core-5.14.0-687.29.1.el9_8, kernel-rt-debug-5.14.0-687.29.1.el9_8 +9
  • RHSA-2026:42919 Released 2026-07-21 · Red Hat rating Important
    kernel security, bug fix, and enhancement update
    • Red Hat Enterprise Linux AppStream (v. 10) kernel-64k-debug-devel-6.12.0-211.37.1.el10_2, kernel-64k-debug-devel-matched-6.12.0-211.37.1.el10_2, kernel-64k-devel-6.12.0-211.37.1.el10_2 +12
    • Red Hat Enterprise Linux BaseOS (v. 10) kernel-6.12.0-211.37.1.el10_2, kernel-64k-6.12.0-211.37.1.el10_2, kernel-64k-core-6.12.0-211.37.1.el10_2 +29
    • Red Hat Enterprise Linux CodeReady Linux Builder (v. 10) kernel-tools-libs-devel-6.12.0-211.37.1.el10_2, libperf-6.12.0-211.37.1.el10_2
    • Red Hat Enterprise Linux Real Time (v. 10) kernel-rt-6.12.0-211.37.1.el10_2, kernel-rt-64k-6.12.0-211.37.1.el10_2, kernel-rt-64k-core-6.12.0-211.37.1.el10_2 +21
    • Red Hat Enterprise Linux Real Time for NFV (v. 10) kernel-rt-6.12.0-211.37.1.el10_2, kernel-rt-core-6.12.0-211.37.1.el10_2, kernel-rt-debug-6.12.0-211.37.1.el10_2 +9

Vendor assessments

Red Hat

Red Hat rating: Important. Red Hat's page for this CVE →

ProductStatusPlan or fix
Red Hat Enterprise Linux for NVIDIA 26AffectedNo fix yet
Red Hat OpenShift Container Platform 4AffectedNo fix yet
Red Hat OpenShift Container Platform 5AffectedNo fix yet
Red Hat Enterprise Linux AppStream (v. 10)Fixed RHSA-2026:42919
Red Hat Enterprise Linux AppStream (v. 9)Fixed RHSA-2026:43307
Red Hat Enterprise Linux AppStream EUS (v. 10.0)Fixed RHSA-2026:44694
Red Hat Enterprise Linux BaseOS (v. 10)Fixed RHSA-2026:42919
Red Hat Enterprise Linux BaseOS (v. 9)Fixed RHSA-2026:43307
Red Hat Enterprise Linux BaseOS EUS (v. 10.0)Fixed RHSA-2026:44694
Red Hat Enterprise Linux CodeReady Linux Builder (v. 10)Fixed RHSA-2026:42919
Red Hat Enterprise Linux CodeReady Linux Builder (v. 9)Fixed RHSA-2026:43307
Red Hat Enterprise Linux CodeReady Linux Builder EUS (v. 10.0)Fixed RHSA-2026:44694
Red Hat Enterprise Linux Real Time (v. 10)Fixed RHSA-2026:42919
Red Hat Enterprise Linux Real Time (v. 9)Fixed RHSA-2026:43307
Red Hat Enterprise Linux Real Time EUS (v. 10.0)Fixed RHSA-2026:44694
Red Hat Enterprise Linux Real Time for NFV (v. 10)Fixed RHSA-2026:42919
Red Hat Enterprise Linux Real Time for NFV (v. 9)Fixed RHSA-2026:43307
Red Hat Enterprise Linux Real Time for NFV EUS (v. 10.0)Fixed RHSA-2026:44694
Not affected: 4 products
  • Red Hat Enterprise Linux 6
  • Red Hat Enterprise Linux 7
  • Red Hat Enterprise Linux 8
  • Red Hat OpenShift Container Platform 4

Timeline

  1. 2026-10-02 Threatist record created from CVE-2026-72123
  2. 2026-10-03 Alias added: GHSA-8862-mgcq-cgrw
  3. 2026-10-09 Fix available: RHSA-2026:44694 · Red Hat
  4. 2026-10-09 Fix available: RHSA-2026:42919 · Red Hat
  5. 2026-10-09 Fix available: RHSA-2026:43307 · Red Hat
  6. 2026-10-09 Fix available: Red Hat Enterprise Linux AppStream (v. 10), Red Hat Enterprise Linux AppStream (v. 9), Red Hat Enterprise Linux AppStream EUS (v. 10.0) +12 · Red Hat
  7. 2026-10-16 Affected versions changed · Red Hat
  8. 2026-10-16 CISA SSVC decision points changed
  9. 2026-10-30 Affected versions changed · Red Hat

References

Other 8

  • TI-2025-26358 tls: fix handling of zero-length records on the rx_list KEVCVSS 3.1CRITICAL 9.8
  • TI-2026-38352 netfilter: bridge: make ebt_snat ARP rewrite writable KEVCVSS 3.1HIGH 8.8
  • TI-2021-02452 Incorrect authorization in Ubuntu linux kernel KEVCVSS 3.1HIGH 8.8
  • TI-2013-05264 The (1) get_user and (2) put_user API functions in the Linux kernel before 3.5.5 on the… KEVCVSS 3.1HIGH 8.8
  • TI-2022-00125 Integer overflow in kernel KEVCVSS 3.1HIGH 8.4
  • TI-2013-01864 The perf_swevent_init function in kernel/events/core.c in the Linux kernel before 3.8.9… KEVCVSS 3.1HIGH 8.4
See all 21727 →

Sources

This product uses the NVD API but is not endorsed or certified by the NVD. Sources and licences