* [CVE-2026-99061][MODERATE 7.0] wifi: brcmfmac: fix P2P device removal race in brcmf_detach()
@ 2026-10-27 5:56 21% AL-KERNEL
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From: AL-KERNEL @ 2026-10-27 5:56 UTC (permalink / raw)
To: kernel-cve
CVE: CVE-2026-99061
Priority: MODERATE 7.0
AL-KERNEL base severity: MODERATE
KPANIC flag: YES
Patch: wifi: brcmfmac: fix P2P device removal race in brcmf_detach()
Commit: 7b79131e357c4786765b20a994ad40d4d35f2163
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=7b79131e357c4786765b20a994ad40d4d35f2163
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-99061
Analysis date: Tue, 27 Oct 2026 01:56:07 -0400
ActionableScore: 1
ActionableScore lower bound: unknown
Actionable bucket: Ordinary Moderate
Manual review required: NO
Summary:
A host administrator racing P2P interface deletion with brcmfmac teardown can cause duplicate unregister of a freed wireless-device object and crash the kernel.
======================================================================
ABOUT THIS REPORT
======================================================================
The original Linux kernel CVE announcement for CVE-2026-99061 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-99061
The original announcement does not normally provide a security severity
estimate, CVSS assessment, or enough information to determine whether the
reported kernel bug represents a practically relevant security issue.
This report was generated by AL-KERNEL, an AI-assisted Linux kernel
vulnerability analysis system developed by Alexander Larkin. It combines
an autonomous classifier with LLM-assisted technical analysis and a
separate ActionableScore mechanism.
The purpose of this report is to prioritize Linux kernel CVEs before
manual review, identify cases that require prompt investigation, and
support automatic closure of issues that are unlikely to have meaningful
security impact.
Published priority for this report: MODERATE 7.0
Manual review required: NO
A detailed explanation of the methodology and priority rules is included
at the end of this message.
======================================================================
AL-KERNEL CLASSIFICATION RESULT
======================================================================
CVE-2026-99061 MODERATE https://www.kernelcve.org/list/?q=CVE-2026-99061 CHECK WITH IMPACT FROM ORIG NN LOW | AEGIS IMPACT MODERATE_KPANIC AEGIS_AS=2 LEGACY=MODERATE_KPANIC RESULT=SAME V39_AEGIS_ONE_STEP_UP=MODERATE->MODERATE_KPANIC (final reconciliation agrees; DECISION: both MODERATE_KPANIC) Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H';CWE-362;*CWE-416;*CWE-672;Other CVSS 'AV:L/AC:H/PR:H/UI:N/S:U/C:L/I:L/A:H';BEST CVSS score: '7';DESCR 'A local race between NL80211_CMD_DEL_INTERFACE and brcmf_detach can remove the same P2P device interface twice after its vif, ifp, and wdev have been freed. The demonstrated primitive is a UAF dereference followed by duplicate list removal at LIST_POISON2, which causes a kernel Oops, while memory reuse could plausibly turn the stale list operation into broader corruption. The base score uses AC:H and PR:H because reliable reproduction requires a narrow concurrency window and normally requires administrative driver removal. For the CVSS the PR:L worst case assumes an attacker controls a network management process and races P2P interface deletion with an independently initiated hot unplug or driver teardown. The issue is local and is not directly reachable through WiFi traffic or a remote network peer. Automated impact decision path. The original SimpleNet classifier selected MODERATE_KPANIC. The primary LLM estimated paranoid CVSS 7 and the production ActionableScore returned 1 with recommendation Ordinary Moderate. The production rules then evaluated CVSS thresholds and ActionableScore thresholds. Recorded rule transitions were ActionableScore thresholds stage MODERATE_KPANIC to MODERATE because the ActionableScore threshold rule was applied. final reconciliation stage MODERATE to MODERATE_KPANIC because the cross model evidence reconciliation rule was applied. The legacy KP specialist has no review artifact for this run. The legacy FD or DH downgrade specialist has no review artifact for this run. Exact triggered rule markers were DECREASED_TO_MODERATEREG_BASED_ON_ACTIONABLESCORELESSTHAN4 and V39_AEGIS_ONE_STEP_UP and MANUAL_REVIEW_REQUIRED. The independent weaker Aegis shadow evaluated CVSS 2.5 and ActionableScore 2 with primitive class CLASS_B and manual review REQUIRED. Its independently reconciled impact was MODERATE_KPANIC. Cross model aggregation changed the production result under an enabled evidence gated merge rule. The final reported impact is MODERATE_KPANIC.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Ordinary Moderate (with actual score 1) MAYBE REMOTE OOB INIT RACE LEAK NETWORK KERNEL_PANIC_PLUS_UAF HARDWARE DECREASED_TO_MODERATEREG_BASED_ON_ACTIONABLESCORELESSTHAN4 KPANIC V39_AEGIS_ONE_STEP_UP MANUAL_REVIEW_REQUIRED - - checked
======================================================================
ACTIONABLESCORE ANALYSIS
======================================================================
ActionableScore=1
PrimitiveClass=CLASS_B
RealUAF=YES
HostAdminRequired=YES
NamespaceScopedPrivilege=NO
ImportantCandidate=NO
ManualReview=RECOMMENDED
AutoDowngradeAllowed=YES
RequiresHostUID0=NO
AuthorizationDecisionBypass=NO
ProtectedResourceImpact=NONE
B4PendingReview=NO
B4PendingConfirmed=NO
1. ActionableScore
* Raw base score: 1.
* Conservative score: 1; no floor or cap applied.
* Raw paranoid score: 1.
* Paranoid score: 1; theoretical allocator reuse is not scoreable evidence.
* Final recommended bucket: **Ordinary Moderate**::
2. Signal breakdown
* +2 Real UAF/lifetime violation: `brcmf_detach()` can unregister and free the P2P `vif`, `ifp`, and `wdev` while `brcmf_p2p_del_vif()` retains the stale object.
* +1 Reliable kernel crash: the later duplicate unregister reaches a second `list_del_rcu()` and faults on `LIST_POISON2`.
* -2 Proven host-admin-equivalent prerequisite: the demonstrated complete trigger removes kernel modules using `rmmod`, requiring effective host `CAP_SYS_MODULE`.
* No hard-race penalty: the 1.5-second firmware-event wait provides a reproducible window rather than evidence of narrow, uncontrollable timing.
* No repeated-release/refcount +1: although unregister is attempted twice, the specifically demonstrated stale operation is duplicate list removal ending in an immediate poison fault, not a shown second refcount/free mutation with surviving leverage. FLOOR 5 therefore does not apply.
* No structured leverage, weak LPE, C/I, or extra availability points: controlled reclaim, attacker-shaped replacement, arbitrary write, disclosure, and boundary bypass are not shown.
3. Reachability analysis
The evidenced sequence requires P2P interface deletion plus driver/module teardown. A network-management process can request `NL80211_CMD_DEL_INTERFACE`, but the demonstrated attacker must also initiate host module removal. Namespace-scoped capability is insufficient for `CAP_SYS_MODULE`. Numeric UID 0 is not intrinsically required because capabilities govern module removal. Hot-unplug by an independent actor is conceivable but does not establish one below-host-admin principal controlling the complete trigger.
4. Primitive and severity reading
This is an active structured-object UAF during teardown, followed by duplicate unregister/list removal. The shown effect is a deterministic host Oops; broader corruption after memory reuse is speculative. It is constrained CLASS_B rather than CLASS_A. ImportantCandidate is NO because no useful post-crash corruption or trust-boundary primitive is demonstrated. Auto-downgrade is allowed given the host-admin trigger and poison-fault-dominated stale use.
5. One-sentence report phrase
A host administrator racing P2P interface deletion with brcmfmac teardown can cause duplicate unregister of a freed wireless-device object and crash the kernel.
6. Manual review advice
MANUAL CHECK RECOMMENDED
Confirm whether any product-specific hot-unplug or device-management path lets a below-host-admin principal trigger teardown.
7. Call-site confidence
Call-site confidence: high
======================================================================
UPSTREAM PATCH SUMMARY
======================================================================
Patch: wifi: brcmfmac: fix P2P device removal race in brcmf_detach()
Commit: 7b79131e357c4786765b20a994ad40d4d35f2163
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=7b79131e357c4786765b20a994ad40d4d35f2163
Commit description:
When the driver is removed while the user space process that created
the P2P device (e.g. wpa_supplicant) is still exiting, the P2P device
interface is removed twice and the kernel crashes.
The two paths are:
- wpa_supplicant, on exit, sends NL80211_CMD_DEL_INTERFACE for the P2P
device. nl80211_del_interface() holds RTNL and the wiphy mutex and
calls brcmf_p2p_del_vif(), which disables discovery and waits up to
1.5 s for BRCMF_E_IF_DEL. Then it calls brcmf_remove_interface(),
which unregisters the wdev and frees the vif and the ifp.
- brcmf_detach() sets the bus down, so BRCMF_E_IF_DEL never arrives,
and calls brcmf_remove_interface(ifp, false) for the same ifp.
brcmf_p2p_ifp_removed() reads ifp->vif and then blocks on
rtnl_lock(). When brcmf_p2p_del_vif() releases RTNL, it calls
cfg80211_unregister_wdev() on the wdev that was already unregistered
and freed.
The second list_del_rcu() of wdev->list faults on LIST_POISON2:
brcmfmac: brcmf_p2p_del_vif delete P2P vif
brcmfmac: brcmf_p2p_deinit_discovery enter
brcmfmac: brcmf_p2p_del_vif P2P: GO_NEG_PHASE status cleared
brcmfmac: brcmf_detach Enter
brcmfmac: brcmf_bus_change_state 1 -> 0
brcmfmac: brcmf_remove_interface Enter, bsscfgidx=1, ifidx=0
brcmfmac: brcmf_del_if Enter, bsscfgidx=1, ifidx=0
brcmfmac: brcmf_p2p_ifp_removed P2P: device interface removed
[1.5 s later, brcmf_p2p_del_vif() timed out]
brcmfmac: brcmf_remove_interface Enter, bsscfgidx=1, ifidx=0
brcmfmac: brcmf_del_if Enter, bsscfgidx=1, ifidx=0
brcmfmac: brcmf_p2p_ifp_removed P2P: device interface removed
Unable to handle kernel paging request at virtual address dead000000000122
Internal error: Oops: 96000044 [#1] PREEMPT_RT SMP
pc : _cfg80211_unregister_wdev+0x6c/0x264 [cfg80211]
Call trace:
_cfg80211_unregister_wdev+0x6c/0x264 [cfg80211]
cfg80211_unregister_wdev+0x10/0x1c [cfg80211]
brcmf_p2p_ifp_removed+0x84/0xb0 [brcmfmac]
brcmf_remove_interface+0x1f4/0x254 [brcmfmac]
brcmf_detach+0x88/0x180 [brcmfmac]
brcmf_sdio_remove+0x90/0x7b0 [brcmfmac]
brcmf_sdiod_remove+0x20/0xa0 [brcmfmac]
brcmf_ops_sdio_remove+0xbc/0x12c [brcmfmac]
sdio_bus_remove+0x38/0x144
device_release_driver_internal+0x1e8/0x2c0
device_release_driver+0x14/0x20
brcmf_sdio_bus_remove+0x2c/0x40 [brcmfmac]
brcmf_fwvid_unregister_vendor+0xd8/0x170 [brcmfmac]
__exit_compat+0x18/0x418 [brcmfmac_cyw]
__arm64_sys_delete_module+0x1ac/0x244
The log was taken with debug=0x406 on an i.MX 8M Plus board with a
CYW55513 (Sona IF513) on SDIO. The driver is the Ezurio backport of
brcmfmac from v6.18.22 on a 5.4-rt kernel. The code involved is the same
in mainline.
To reproduce:
1. Start wpa_supplicant on wlan0 and let it associate. It creates the
P2P device (iw dev shows "type P2P-device").
2. Stop wpa_supplicant and remove the driver without waiting for
wpa_supplicant to exit:
kill $(pidof wpa_supplicant)
rmmod brcmfmac_cyw brcmfmac
The crash is reproducible on that board.
For the interface without a netdev (the P2P device), take RTNL and the
wiphy mutex in brcmf_detach() before reading iflist, and remove it with
locked=true. If brcmf_p2p_del_vif() runs first, brcmf_detach() finds the
slot empty. If brcmf_detach() runs first, nl80211 does not find the wdev
any more. The interfaces with a netdev are removed as before, because
brcmf_del_if() takes RTNL on its own for the primary interface.
Fixes: 9831bcb ("brcmfmac: Deleting of p2p device is leaking memory.")
Cc: [email protected]
Assisted-by: claude-opus-5-5
[Commit description truncated; see the upstream URL below]
Changed files:
drivers/net/wireless/broadcom/brcm80211/brcmfmac/core.c
Diff excerpt:
Not included in this email. See the upstream URL for the full patch.
Full patch:
https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=7b79131e357c4786765b20a994ad40d4d35f2163
======================================================================
DETAILED REPORT METHODOLOGY
======================================================================
The original Linux kernel CVE announcement for CVE-2026-99061 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-99061
The original CVE announcement normally does not include a security-level
estimate. In particular, it may not contain a CVSS assessment, an impact
level, or enough information to determine whether the reported bug is a
practically relevant security issue. One purpose of this parallel CVE list
is to provide that missing technical and prioritization information.
The original goal of the AL-KERNEL project was to prioritize Linux kernel
CVE analysis automatically before manual review. The system can also help
identify non-security issues that may be suitable for automatic closure.
This report was generated by AL-KERNEL, an AI-assisted Linux kernel
vulnerability analysis system developed by Alexander Larkin.
The first analysis stage combines an autonomous classifier with additional
LLM-based analysis. The autonomous classifier runs locally on a CPU and is
based on a backpropagation neural network. Together, these mechanisms
produce a technical vulnerability description, identify likely weakness
types, estimate CVSS severity, and provide input for ActionableScore.
Two CVSS estimates are retained because incomplete kernel vulnerability
information often permits more than one defensible interpretation:
Conservative CVSS vector: AV:L/AC:H/PR:H/UI:N/S:U/C:L/I:L/A:H
The Best / paranoid CVSS vector: AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H
The Best / paranoid CVSS score: 7
The conservative vector represents a lower-impact interpretation.
The Best/paranoid vector intentionally represents a plausible upper-bound
interpretation and should not automatically be treated as demonstrated
real-world impact.
CVSS may also need to be adjusted for a particular Linux deployment,
because actual reachability, privileges, enabled kernel configuration,
hardware, namespaces, exposed device nodes, and other environmental
conditions can differ significantly between systems.
A separate ActionableScore mechanism evaluates practical remediation
urgency. Its analysis may include reachability, attack prerequisites,
subsystem exposure, memory-corruption characteristics, denial-of-service
reliability, and possible confidentiality, integrity, or
privilege-escalation impact.
Conservative ActionableScore: unknown
Paranoid ActionableScore: 1
The final base severity is taken directly from the second tab-separated
field of the AL-KERNEL classification result. ActionableScore does not
replace or independently override that final AL-KERNEL decision, and
if ActionableScore adjusted impact level of ALKERNEL, then you would see
self-readable flags above like INCREASED_TO_HIGH_BASED_ON_ACTIONABLESCOREHIGHEREQTHAN7.
For an AL-KERNEL result of MODERATE, this report uses the following
additional presentation split:
ActionableScore below 5 -> MODERATE REGULAR
ActionableScore 5 or more -> MODERATE 7.0
The distinction between MODERATE REGULAR and MODERATE 7.0 makes it
possible to identify Moderate issues that should receive manual analysis
and fixes before lower-priority MODERATE REGULAR issues. In many cases,
MODERATE REGULAR fixes may wait for a later rebase or routine update.
There is one override in which MODERATE REGULAR becomes MODERATE 7.0
even when the ActionableScore is below 5. When the AL-KERNEL result
contains the KPANIC flag, a MODERATE result is always presented as
MODERATE 7.0. The KPANIC flag selected with few regexps without
usage of AI at all, so it helps to detect cases when Kernel Crash happens
and similar (to filter False-Negative results from the LLM usage).
KPANIC indicates that a reliable kernel crash, kernel panic, or similarly
serious kernel availability impact was identified by the classification
workflow.
AL-KERNEL base severity for this report: MODERATE
KPANIC detected for this report: YES
Published priority for this report (same as in Subject): MODERATE 7.0
These results are intended to support engineering triage. They are
machine-generated estimates, and cases marked for manual review should
be validated by a human security engineer before final disposition.
For more info read docs linked from here: https://kernelcve.org/
(and you can submit you own patch there to generate such a report
for non-existant CVE-id yet).
Note that in many cases this AI tool selects higher severity, than
real is (means you can expect Importants instead of Moderate 7.0 or
Moderates 7.0 instead of regular Moderates). If you see such cases,
please use reply email interface to add additional manual analyses
info to this particular CVE.
And please, please, let me know when you see Lows instead of Importants
or Important instead of Low (because particular for such cases I
need to tune this AI tool to make it better for this one and next similar).
My contact email for such notifications is [email protected] (and both
send reply to CVE record itself too and see "reply" button below for howto reply).
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