NVD / CVE Program· CNA Linux

CVE-2025-39863: wifi: brcmfmac: fix use-after-free when rescheduling brcmf_btcoex_info work

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 2f6fbc8e04ca1d1d5c560be694199f847229c625, 3e789f8475f6c857c88de5c5bf4b24b11a477dd7, 9cb83d4be0b9b697eae93d321e0da999f9cdfcfc; azl3 kernel 6.6.104.2-4 on Azure Linux 3.0 6.6.112.1-1; cbl2 kernel 5.15.202.1-1 on CBL-Mariner 2.0 Release Notes.

Low priority for now. Upgrade to Linux Linux 2f6fbc8e04ca1d1d5c560be694199f847229c625, 3e789f8475f6c857c88de5c5bf4b24b11a477dd7, 9cb83d4be0b9b697eae93d321e0da999f9cdfcfc; azl3 kernel 6.6.104.2-4 on Azure Linux 3.0 6.6.112.1-1; cbl2 kernel 5.15.202.1-1 on CBL-Mariner 2.0 Release Notes 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: wifi: brcmfmac: fix use-after-free when rescheduling brcmf_btcoex_info work The brcmf_btcoex_detach() only shuts down the btcoex timer, if the flag timer_on is false. However, the brcmf_btcoex_timerfunc(), which runs as timer handler, sets timer_on to false. This creates critical race conditions: 1.If brcmf_btcoex_detach() is called while brcmf_btcoex_timerfunc() is executing, it may observe timer_on as false and skip the call to timer_shutdown_sync(). 2.The brcmf_btcoex_timerfunc() may then reschedule the brcmf_btcoex_info worker after the cancel_work_sync() has been executed, resulting in use-after-free bugs. The use-after-free bugs occur in two distinct scenarios, depending on the timing of when the brcmf_btcoex_info struct is freed relative to the execution of its worker thread. Scenario 1: Freed before the worker is scheduled The brcmf_btcoex_info is deallocated before the worker is scheduled. A race condition can occur when schedule_work(&bt_local->work) is called after the target memory has been freed. The sequence of events is detailed below: CPU0 | CPU1 brcmf_btcoex_detach | brcmf_btcoex_timerfunc | bt_local->timer_on = false; if (cfg->btcoex->timer_on) | ... | cancel_work_sync(); | ... | kfree(cfg->btcoex); // FREE | | schedule_work(&bt_local->work); // USE Scenario 2: Freed after the worker is scheduled The brcmf_btcoex_info is freed after the worker has been scheduled but before or during its execution. In this case, statements within the brcmf_btcoex_handler() — such as the container_of macro and subsequent dereferences of the brcmf_btcoex_info object will cause a use-after-free access. The following timeline illustrates this scenario: CPU0 | CPU1 brcmf_btcoex_detach | brcmf_btcoex_timerfunc | bt_local->timer_on = false; if (cfg->btcoex->timer_on) | ... | cancel_work_sync(); | ... | schedule_work(); // Reschedule | kfree(cfg->btcoex); // FREE | brcmf_btcoex_handler() // Worker /* | btci = container_of(....); // USE The kfree() above could | ... also occur at any point | btci-> // USE during the worker's execution| */ | To resolve the race conditions, drop the conditional check and call timer_shutdown_sync() directly. It can deactivate the timer reliably, regardless of its current state. Once stopped, the timer_on state is then set to false.

HighCVSS 7.8 · v3.1—No exploit Fix available

BDU:2025-13447

Published: Sep 19, 2025
Updated: Oct 19, 2026
EPSS: 0.1% · 5th percentile
CWE: CWE-416

Report tools

JSON

Action score

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: 7.8
CNA · Linux: 7.8; agree

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

Get told when this record changes

Not in KEV: no record of exploitation in the wild
No public exploit code on record
A fix has been released

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Noroxi analysis

What does it mean in your environment?

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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.

Vendor	Product	CPE
linux	linux kernel	cpe:2.3:o:linux:linux_kernel

Affected versions

NVD version ranges (for catalog products). Add the product to your stack with a version and matching uses these.

linux linux kernel3.10 and later · before 6.6.105
linux linux kernel6.7 and later · before 6.12.46
linux linux kernel6.13 and later · before 6.16.6
linux linux kernel6.17

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
- 3.10affected
- 61730d4dfffc2cc9d3a49fad87633008105c18ba and later · before c75600e69e66a751cc046cd9c407b942f298d852affected · git
- 61730d4dfffc2cc9d3a49fad87633008105c18ba and later · before ae58f70bde0433f27ef4b388ab50634736607bf6affected · git
- 61730d4dfffc2cc9d3a49fad87633008105c18ba and later · before f1150153c4e5940fe49ab51136343c5b4fe49d63affected · git
- 61730d4dfffc2cc9d3a49fad87633008105c18ba and later · before 3e789f8475f6c857c88de5c5bf4b24b11a477dd7affected · git
- 61730d4dfffc2cc9d3a49fad87633008105c18ba and later · before 2f6fbc8e04ca1d1d5c560be694199f847229c625affected · git
- 61730d4dfffc2cc9d3a49fad87633008105c18ba and later · before 9cb83d4be0b9b697eae93d321e0da999f9cdfcfcaffected · git
- before 3.10not affected · semver
- 5.15.210 and later · up to and including 5.15.*not affected · semver
- 6.1.167 and later · up to and including 6.1.*not affected · semver

Package-level exposure

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

Ecosystem	Package	Affected range	Fix
Debian:12	linux	before 6.1.170-1	6.1.170-1
Debian:13	linux	before 6.12.48-1	6.12.48-1
Debian:14	linux	before 6.16.6-1	6.16.6-1

Same product

linux: all records

Other highest-scoring records for the same primary product.

CVE-2026-31431crypto: algif_aead - Revert to operating out-of-placeKEV
90Now
CVE-2022-0847A flaw was found in the way the "flags" member of the new pipe buffer structure was lacking proper initialization in copy_page_to_iter_pipe KEV
89Now
CVE-2021-22555Heap Out-Of-Bounds Write in Netfilter IP6T_SO_SET_REPLACEKEV
85Now

Published before and after this one in the same product

← EarlierCVE-2025-39861Sep 19, 2025 · Bluetooth: vhci: Prevent use-after-free by removing debugfs files early
31Monitor
← EarlierCVE-2025-39862Sep 19, 2025 · wifi: mt76: mt7915: fix list corruption after hardware restart
31Monitor
Later →CVE-2025-39864Sep 19, 2025 · wifi: cfg80211: fix use-after-free in cmp_bss()
31Monitor

Remediation

Which version to upgrade to

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

Product / package	Fixed version	Source
Linux Linux	2f6fbc8e04ca1d1d5c560be694199f847229c625	Vendor (CNA)
Linux Linux	3e789f8475f6c857c88de5c5bf4b24b11a477dd7	Vendor (CNA)
Linux Linux	9cb83d4be0b9b697eae93d321e0da999f9cdfcfc	Vendor (CNA)
Linux Linux	ae58f70bde0433f27ef4b388ab50634736607bf6	Vendor (CNA)
Linux Linux	c75600e69e66a751cc046cd9c407b942f298d852	Vendor (CNA)
Linux Linux	f1150153c4e5940fe49ab51136343c5b4fe49d63	Vendor (CNA)
azl3 kernel 6.6.104.2-4 on Azure Linux 3.0	6.6.112.1-1 · CBL-Mariner Releases	Microsoft (MSRC)
cbl2 kernel 5.15.202.1-1 on CBL-Mariner 2.0	Release Notes	Microsoft (MSRC)
debian:linux	6.1.170-1 · Debian:12	Package registry (OSV)

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.

No history yet (it accumulates with the daily EPSS job).

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)

CWE-416 · Use After Free

CVSS vector

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

nvd-primary

Root cause

After a memory region is freed, another reference pointing to it is still used. By then, the same region may have been allocated for different data.

The bug in code

The whole CWE-416 class

A representative example of this vulnerability class. Not the vendor's source code; it shows the faulty pattern and its fix.

Vulnerable

1free(dev->buf);
2/* ... another thread is still running ... */
3process(dev->buf);

Fixed

1lock(&dev->lock);
2free(dev->buf);
3dev->buf = NULL;
4unlock(&dev->lock);

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

Fix✗ → ✓Sep 28, 2026, 10:10 PM UTC

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

References

git.kernel.org/stable/c/2f6fbc8e04ca1d1d5c560be694199f847229c625

Show all references (6 more)

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

All records