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NVD / CVE Program· CNA Linux

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

Noroxi assessment

Priority: Monitor (action score 31/100)

  • The sources we track (CISA KEV, Exploit-DB, Metasploit, Nuclei, GitHub) show no public exploit code or exploitation in the wild.
  • Probability of exploitation in the next 30 days: 0.16% (FIRST EPSS).
  • Someone with local access to the system can trigger it. A low-privileged account is enough. No user action is required. No special conditions are required; it is repeatable.
  • Fixed version: Linux Linux 036a8c320ca11bc912e8027adcfad14b326f067e, 3cf4fd5316f449811d8baf1bc6978ef5a7b743a9, 4.20.

Low priority for now. Upgrade to Linux Linux 036a8c320ca11bc912e8027adcfad14b326f067e, 3cf4fd5316f449811d8baf1bc6978ef5a7b743a9, 4.20 or later.

Generated automatically from the record's data: CVSS (NVD and CNA), CISA KEV and SSVC, FIRST EPSS, exploit sources, fixed versions. How we calculate it

Primary sources: NVD · CVE.org · FIRST EPSS

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.

HighCVSS 7.8 · v3.1—No exploit Fix available
Published
Aug 15, 2026
Updated
Oct 16, 2026
EPSS
0.1% · 6th percentile
CWE
—

Report tools

JSON

Action score

31

Monitor

Low priority for now.

CVSS
31 / 40 · 7.8 / 10
CISA KEV
0 / 30 · Not listed
EPSS
0 / 30 · 0.1%

CISA SSVC decision

Exploitation
none
Automatable
no
Technical impact
total

Vulnrichment: CISA's decision-tree inputs.

CNA vs NVD score

NVD
—
CNA · Linux
7.8
NVD has not scored this yet; the score shown is the CNA’s.

The score given by the assigning authority versus NVD’s independent score. A gap means the severity is contested.

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Noroxi analysis

What does it mean in your environment?

The assessment above is generated automatically from the record's data; it doesn't know your environment. Our team verifies on your systems whether this vulnerability is actually exploitable and which mitigation is enough.

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Affected systems

Is your version affected?

Pick the product and type the version you run. It's compared with this record's version ranges in your browser; the version isn't sent anywhere.

—

Versions reported by the vendor

Affected version ranges reported by the assigning authority (Linux). Independent of NVD's CPE analysis and usually ahead of it.

  • Linux Linux

    • fbac09a3b8890003c0c55294c00709f3ae5501bb, 5b48f5711f1c630841ab78dcc061de902f0e37bf, edb4baffb9483141a50fb7f7146cfe4a4c0c2db8, 5.19affected
    • 85cd41070df992d3c0dfd828866fdd243d3b774a and later · before de5fce46637de05bef56ec08528127676eb6fc9baffected · git
    • f34f2a18e47b73e48f90a757e1f4aaa8c7d665a1 and later · before 036a8c320ca11bc912e8027adcfad14b326f067eaffected · git
    • f1b4e32aca0811aa011c76e5d6cf2fa19224b386 and later · before 3cf4fd5316f449811d8baf1bc6978ef5a7b743a9affected · git
    • f1b4e32aca0811aa011c76e5d6cf2fa19224b386 and later · before 4177762f70646ac48a2af382e45a795cbd295198affected · git
    • f1b4e32aca0811aa011c76e5d6cf2fa19224b386 and later · before 6fd08e8d826c3aa4cc7021f5f9cdbb7fa7441d3faffected · git
    • f1b4e32aca0811aa011c76e5d6cf2fa19224b386 and later · before cd830e0bc25ee2d38cbfbdbb3cd77c5f53b2b6d5affected · git
    • f1b4e32aca0811aa011c76e5d6cf2fa19224b386 and later · before ce2d4b121fb7545e1ed588e860c8e5fd5ad45224affected · git
    • f1b4e32aca0811aa011c76e5d6cf2fa19224b386 and later · before 68973f9db76144825e4f35dfdc80fb8279eb2d57affected · git
    • 5.10.130 and later · before 5.10.265affected · semver

Package-level exposure

OSV and GitHub Advisory data: ecosystem, package and range. SBOM matching uses this table.

EcosystemPackageAffected rangeFix
AlmaLinux:10kernelbefore 6.12.0-211.37.1.el10_26.12.0-211.37.1.el10_2
AlmaLinux:10kernel-64kbefore 6.12.0-211.37.1.el10_26.12.0-211.37.1.el10_2
AlmaLinux:10kernel-64k-corebefore 6.12.0-211.37.1.el10_26.12.0-211.37.1.el10_2
AlmaLinux:10kernel-64k-debugbefore 6.12.0-211.37.1.el10_26.12.0-211.37.1.el10_2
AlmaLinux:10kernel-64k-debug-corebefore 6.12.0-211.37.1.el10_26.12.0-211.37.1.el10_2
AlmaLinux:10kernel-64k-debug-develbefore 6.12.0-211.37.1.el10_26.12.0-211.37.1.el10_2
AlmaLinux:10kernel-64k-debug-devel-matchedbefore 6.12.0-211.37.1.el10_26.12.0-211.37.1.el10_2
AlmaLinux:10kernel-64k-debug-modulesbefore 6.12.0-211.37.1.el10_26.12.0-211.37.1.el10_2
AlmaLinux:10kernel-64k-debug-modules-corebefore 6.12.0-211.37.1.el10_26.12.0-211.37.1.el10_2
AlmaLinux:10kernel-64k-debug-modules-extrabefore 6.12.0-211.37.1.el10_26.12.0-211.37.1.el10_2
AlmaLinux:10kernel-64k-develbefore 6.12.0-211.37.1.el10_26.12.0-211.37.1.el10_2
AlmaLinux:10kernel-64k-devel-matchedbefore 6.12.0-211.37.1.el10_26.12.0-211.37.1.el10_2
AlmaLinux:10kernel-64k-modulesbefore 6.12.0-211.37.1.el10_26.12.0-211.37.1.el10_2
AlmaLinux:10kernel-64k-modules-corebefore 6.12.0-211.37.1.el10_26.12.0-211.37.1.el10_2
AlmaLinux:10kernel-64k-modules-extrabefore 6.12.0-211.37.1.el10_26.12.0-211.37.1.el10_2
AlmaLinux:10kernel-abi-stablelistsbefore 6.12.0-211.37.1.el10_26.12.0-211.37.1.el10_2
AlmaLinux:10kernel-corebefore 6.12.0-211.37.1.el10_26.12.0-211.37.1.el10_2
AlmaLinux:10kernel-cross-headersbefore 6.12.0-211.37.1.el10_26.12.0-211.37.1.el10_2
AlmaLinux:10kernel-debugbefore 6.12.0-211.37.1.el10_26.12.0-211.37.1.el10_2
AlmaLinux:10kernel-debug-corebefore 6.12.0-211.37.1.el10_26.12.0-211.37.1.el10_2
AlmaLinux:10kernel-debug-develbefore 6.12.0-211.37.1.el10_26.12.0-211.37.1.el10_2
AlmaLinux:10kernel-debug-devel-matchedbefore 6.12.0-211.37.1.el10_26.12.0-211.37.1.el10_2
AlmaLinux:10kernel-debug-modulesbefore 6.12.0-211.37.1.el10_26.12.0-211.37.1.el10_2
AlmaLinux:10kernel-debug-modules-corebefore 6.12.0-211.37.1.el10_26.12.0-211.37.1.el10_2

+96

Same product

linux: all records

Other highest-scoring records for the same primary product.

  • CVE-2026-74705udp: fix potential use-after-free in tunnel segmentation
    40Plan
  • CVE-2026-74612veth: fix skb length accounting after XDP frag adjustment
    40Plan
  • CVE-2026-74475vxlan: use neigh_ha_snapshot() in route_shortcircuit()
    40Plan

Published before and after this one in the same product

  • ← EarlierCVE-2026-72121Aug 15, 2026 · can: bcm: add locking when updating filter and timer values
    35Monitor
  • ← EarlierCVE-2026-72122Aug 15, 2026 · can: bcm: fix lockless bound/ifindex race and silent RX_SETUP failure
    29Monitor
  • Later →CVE-2026-72124Aug 15, 2026 · can: isotp: serialize TX state transitions under so->rx_lock
    35Monitor

Remediation

Which version to upgrade to

Fix versions compiled from the vendor, package registries and Microsoft. Verify the vendor's note before upgrading.

Product / packageFixed versionSource
Linux Linux036a8c320ca11bc912e8027adcfad14b326f067eVendor (CNA)
Linux Linux3cf4fd5316f449811d8baf1bc6978ef5a7b743a9Vendor (CNA)
Linux Linux4.20Vendor (CNA)
Linux Linux4177762f70646ac48a2af382e45a795cbd295198Vendor (CNA)
Linux Linux5.10.265Vendor (CNA)
Linux Linux5.15.216Vendor (CNA)
Linux Linux5.19Vendor (CNA)
Linux Linux5.5Vendor (CNA)
Linux Linux68973f9db76144825e4f35dfdc80fb8279eb2d57Vendor (CNA)
Linux Linux6fd08e8d826c3aa4cc7021f5f9cdbb7fa7441d3fVendor (CNA)
Linux Linuxcd830e0bc25ee2d38cbfbdbb3cd77c5f53b2b6d5Vendor (CNA)
Linux Linuxce2d4b121fb7545e1ed588e860c8e5fd5ad45224Vendor (CNA)
Linux Linuxde5fce46637de05bef56ec08528127676eb6fc9bVendor (CNA)
almalinux:kernel6.12.0-211.37.1.el10_2 · AlmaLinux:10Package registry (OSV)
almalinux:kernel-64k6.12.0-211.37.1.el10_2 · AlmaLinux:10Package registry (OSV)
almalinux:kernel-64k-core6.12.0-211.37.1.el10_2 · AlmaLinux:10Package registry (OSV)
almalinux:kernel-64k-debug6.12.0-211.37.1.el10_2 · AlmaLinux:10Package registry (OSV)
almalinux:kernel-64k-debug-core6.12.0-211.37.1.el10_2 · AlmaLinux:10Package registry (OSV)
almalinux:kernel-64k-debug-devel6.12.0-211.37.1.el10_2 · AlmaLinux:10Package registry (OSV)
almalinux:kernel-64k-debug-devel-matched6.12.0-211.37.1.el10_2 · AlmaLinux:10Package registry (OSV)
almalinux:kernel-64k-debug-modules6.12.0-211.37.1.el10_2 · AlmaLinux:10Package registry (OSV)
almalinux:kernel-64k-debug-modules-core6.12.0-211.37.1.el10_2 · AlmaLinux:10Package registry (OSV)
almalinux:kernel-64k-debug-modules-extra6.12.0-211.37.1.el10_2 · AlmaLinux:10Package registry (OSV)
almalinux:kernel-64k-devel6.12.0-211.37.1.el10_2 · AlmaLinux:10Package registry (OSV)
almalinux:kernel-64k-devel-matched6.12.0-211.37.1.el10_2 · AlmaLinux:10Package registry (OSV)
debian:linux6.1.180-1 · Debian:12Package registry (OSV)
red hat:kernel-64k-debug-debuginfo0:6.12.0-211.37.1.el10_2 · Red Hat:enterprise_linux:10.2Package registry (OSV)
red hat:kernel-64k-debug-devel0:6.12.0-211.37.1.el10_2 · Red Hat:enterprise_linux:10.2Package registry (OSV)
red hat:kernel-64k-debug-devel-matched0:6.12.0-211.37.1.el10_2 · Red Hat:enterprise_linux:10.2Package registry (OSV)
red hat:kernel-64k-debuginfo0:6.12.0-211.37.1.el10_2 · Red Hat:enterprise_linux:10.2Package registry (OSV)

+8

Exploit status

No known public exploit

No public exploit has been observed yet. That doesn't mean you're safe, only that the bar is a little higher.

Research context

For pentesters and researchers: attack profile, score disagreement, timeline, patch commits, credits, variant and chain candidates, bug bounty scope. All derived from existing data; no exploit code.

Timeline

From publication to today: proof of concept, Metasploit module, CISA KEV and fix record. Dates are as reported by the sources.

No dated events beyond publication.

EPSS, last 120 days

FIRST EPSS daily score; only changes of 0.01 or more are recorded (step chart).

Patch and commit links

Commit, PR and diff links among the references. A starting point for patch-diffing and variant hunting; fixes, not exploits.

No commit or PR link among the references.

Credits

All researchers

Finders, reporters and analysts named in the CNA record. Click a name for that researcher’s other records.

No credits in the CNA record.

Variant candidates

Same product, same weakness class, within 18 months. If the patch missed the root cause, the sibling bug is here.

No nightly-computed relations.

Chain candidates

An authentication bypass and a privilege-requiring bug in the same product, published close together: combined they may become an unauthenticated path.

—

Bug bounty scope

No known public program.

Source: bounty-targets-data (public HackerOne, Bugcrowd, Intigriti, YesWeHack listings).

Technical details

Attack conditions

  • Someone with local access to the system can trigger it.
  • A low-privileged account is enough.
  • No user action is required.
  • No special conditions are required; it is repeatable.

If successful

Confidentiality
high · data can be read
Integrity
high · data or configuration can be modified
Availability
high · the service can be disrupted
Attack vector
Local
Attack complexity
Low
Privileges required
Low
User interaction
None
Scope
Unchanged
Confidentiality impact
High
Integrity impact
High
Availability impact
High

Weakness class (CWE)

—

CVSS vector

CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

nvd-secondary

Attack context

MITRE CAPEC attack patterns and ATT&CK techniques for this weakness class (CWE). A starting point for detection rules and threat hunting.

MITRE has no CAPEC/ATT&CK mapping for this CWE.

Change log

  1. SSVC exploitation— → none
  2. Fix✗ → ✓

For records you follow, these changes also arrive as notifications. →

References

Show all references (7 more)

Vendor advisories and official records. Exploit/PoC links are deliberately left out.

All records