[CVE-2026-74505][MODERATE 7.0] ALSA: 6fire: Fix UAF at error handling during probe

[CVE-2026-74505][MODERATE 7.0] ALSA: 6fire: Fix UAF at error handling during probe

[AL-KERNEL]

CVE: CVE-2026-74505
Priority: MODERATE 7.0
AL-KERNEL base severity: MODERATE
KPANIC flag: NO
Patch: ALSA: 6fire: Fix UAF at error handling during probe
Commit: 49bc7741cd2761c703a292dc69245041ae8a67bd
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=49bc7741cd2761c703a292dc69245041ae8a67bd
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-74505
Analysis date: Sat, 15 Aug 2026 14:41:21 -0400
ActionableScore: 5
ActionableScore lower bound: 4
Actionable bucket: Actionable Moderate at minimum
Manual review required: YES

Summary:
A pending URB in the ALSA 6fire probe error path may complete after device resources are freed, causing a UAF that is realistically a physical-device-triggered kernel DoS and requires manual review for possible memory corruption impact.

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ABOUT THIS REPORT
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The original Linux kernel CVE announcement for CVE-2026-74505 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-74505

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: YES

A detailed explanation of the methodology and priority rules is included
at the end of this message.

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AL-KERNEL CLASSIFICATION RESULT
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CVE-2026-74505	MODERATE	CHECK WITH IMPACT FROM ORIG NN LOW	Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:P/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H';*CWE-416;CWE-362;*CWE-664;Other CVSS 'AV:P/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H';BEST CVSS score: '6.4';DESCR 'A use-after-free can occur in the ALSA 6fire USB driver during probe error handling because device resources may be freed while a URB is still pending. A malicious or faulty USB device can drive the probe into the error path and later completion of the pending URB may access freed driver state, causing a kernel crash and possibly memory corruption. For the CVSS the PR:N is used for the paranoid score because a physical USB attacker does not need a local account on the victim system to trigger device probing. The issue is not network reachable. Base impact is denial of service, while the paranoid impact uses C:H/I:H/A:H because asynchronous URB UAF is a memory corruption class that can justify manual review for possible privilege escalation.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Actionable Moderate at minimum (with actual score 5)	YES	USB INIT ERRORPATH UAF HARDWARE LINUS  DECREASED_TO_MODERATEREG_BASED_ON_FALSEPOSCHECKOFKP	NO	NO	checked

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ACTIONABLESCORE ANALYSIS
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ActionableScore=5
ActionableScoreLower=4

## 1. ActionableScore

* Conservative score: 4
* Paranoid score: 5
* Final recommended bucket: **Actionable Moderate at minimum**::

## 2. Signal breakdown

Triggered signals:

* Generic memory corruption: +2
  The commit explicitly says a pending URB may survive resource freeing and lead to UAF.

* Real lifetime corruption: +1
  This is an async USB URB lifetime mismatch in probe error handling.

* Reliable kernel crash / strong DoS: +1
  A completion path using freed driver state can realistically crash the kernel.

* Privileged kernel/device-management memory corruption path: +1
  The bug is in USB device probe and URB cleanup logic, a trusted driver/device-management path.

* Weak LPE concern: +1, paranoid only
  UAF in asynchronous URB completion can theoretically become exploitable after heap reuse, but no controlled reclaim, callback control, or overwrite primitive is shown.

Subtracted signals:

* Physical-only or rare hardware-only condition: -2
  Realistic triggering requires a malicious or faulty USB device, USB emulation, or physical/device-level access.

* Corruption primitive highly constrained or no demonstrated attacker-controlled reuse: -1
  The patch does not show attacker-controlled reclaim, controlled object replacement, arbitrary write, or function pointer control.

Call-site confidence: medium. The relevant probe error path and cleanup calls are shown, but the URB completion users and exact freed object accesses are not included in the provided diff.

## 3. Reachability analysis

The bug can be triggered during probing of the ALSA 6fire USB device when probe fails after an URB has been submitted but before resources are fully initialized. A malicious or malfunctioning USB device could influence the probe and error path. No local Linux user account is required for a physical USB attacker, so PR:N is reasonable for CVSS physical-vector interpretation. This is not network reachable. Containers and namespaces do not materially lower the requirement because the trigger is device attachment/probing rather than a namespaced userspace API. Exposure is limited because the affected driver and hardware are not broad default attack surfaces.

## 4. Severity interpretation

This is not an ordinary bookkeeping bug because the commit explicitly identifies a UAF caused by a pending URB after resource free. Realistic impact is most likely kernel crash or host DoS from a malicious or faulty USB device. Theoretical memory corruption and privilege escalation cannot be excluded because async UAF bugs can sometimes be shaped through heap reuse, but the provided patch does not demonstrate a strong exploit primitive. Therefore it is best treated as Actionable Moderate rather than auto-closed Low or strong Important.

## 5. One-sentence report phrase

A pending URB in the ALSA 6fire probe error path may complete after device resources are freed, causing a UAF that is realistically a physical-device-triggered kernel DoS and requires manual review for possible memory corruption impact.

## 6. Manual review recommendation

MANUAL CHECK REQUIRED

Reason: this is an explicit UAF in asynchronous USB URB lifetime handling. Even though exposure is physical and exploitability is constrained, kernel UAF bugs should not be auto-closed without manual review.

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UPSTREAM PATCH SUMMARY
======================================================================

Patch: ALSA: 6fire: Fix UAF at error handling during probe
Commit: 49bc7741cd2761c703a292dc69245041ae8a67bd
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=49bc7741cd2761c703a292dc69245041ae8a67bd

Commit description:

Although 6fire driver had a few fixes for dealing with the early error
handling during the probe phase, it forgot a pending URB before
freeing the resources, which may lead to a UAF.

This patch addresses it by doing the almost same cleanup procedure
like the normal disconnect phase at the error path.

Reported-and-tested-by: Shuangpeng Bai <shuangpeng.kernel@gmail.com>
Closes: https://lore.kernel.org/20260724030900.1984491-1-shuangpeng.kernel@gmail.com
Cc: <stable@vger.kernel.org>
Link: https://patch.msgid.link/20260726074821.2288158-1-tiwai@suse.de
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Changed files:
  sound/usb/6fire/chip.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=49bc7741cd2761c703a292dc69245041ae8a67bd

======================================================================
DETAILED REPORT METHODOLOGY
======================================================================

The original Linux kernel CVE announcement for CVE-2026-74505 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-74505

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:P/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H
  The Best / paranoid CVSS vector: AV:P/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H
  The Best / paranoid CVSS score: 6.4

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: 4
  Paranoid ActionableScore: 5

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: NO
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 alexanjelausa@gmail.com (and both
send reply to CVE record itself too and see "reply" button below for howto reply).