From: AL-KERNEL <[email protected]>
To: [email protected]
Subject: [CVE-2026-46048][LOW] ALSA: caiaq: fix usb_dev refcount leak on probe failure
Date: Wed, 27 May 2026 15:21:43 -0400 [thread overview]
Message-ID: <[email protected]> (raw)
CVE: CVE-2026-46048
Priority: LOW
AL-KERNEL base severity: LOW
KPANIC flag: NO
Patch: ALSA: caiaq: fix usb_dev refcount leak on probe failure
Commit: 50c6a1f05973f56d23280c9d7645a7a5734e0907
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=50c6a1f05973f56d23280c9d7645a7a5734e0907
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-46048
Analysis date: Wed, 27 May 2026 15:21:43 -0400
ActionableScore: 0
ActionableScore lower bound: unknown
Actionable bucket: Ordinary Moderate / Low-like
Manual review required: NO
Summary:
No one-sentence report phrase was found.
======================================================================
ABOUT THIS REPORT
======================================================================
The original Linux kernel CVE announcement for CVE-2026-46048 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-46048
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: LOW
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-2026-46048 LOW CHECK Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:P/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H';*CWE-401;*CWE-772;CWE-404;CWE-459;Other CVSS 'AV:P/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:L';BEST CVSS score: '4.3';DESCR 'ALSA caiaq can leak a usb_device reference when probe fails before card private_free is installed. A malformed USB audio device can make init_card fail after usb_get_dev(), so snd_card_free() does not call card_free() and the usb reference plus related allocations remain leaked. For the CVSS the PR:N is used because no software privileges are needed once the malicious device is attached, but the vector is physical and normally requires user interaction or device insertion. The issue is not network reachable and does not provide a memory corruption primitive. Impact is resource exhaustion denial of service only if probe failures are repeated.';NO MANUAL CHECK; ,and ActionableScore result is Ordinary Moderate / Low-like (with actual score 0) SKIP CVE-2026-46048 SKIP The Fixes patch not applied yet, so unlikely that actual: 80bb50e2d459213cccff3111d5ef98ed4238c0d5 YES NO NO unknown MAYBE USB INIT PRINTF-TTY LEAK ERRORPATH HARDWARE LINUS SYZBOT - - checked
======================================================================
ACTIONABLESCORE ANALYSIS
======================================================================
ActionableScore=0
1. ActionableScore
* Conservative score: 0
* Paranoid score: 0
* Final recommended bucket: **Ordinary Moderate / Low-like**::
2. Signal breakdown
* Availability/resource leak concern: +1. A failed probe can leak a `usb_device` reference and related allocations.
* Physical-only trigger: -2. Realistic triggering requires attaching or emulating a malformed USB audio device.
* Rare and driver-specific exposure: -1. This affects the ALSA `caiaq` USB driver and a probe-failure path, not a broad default kernel interface.
* No memory corruption signal. The patch fixes a missing destructor assignment for reference cleanup, not UAF, double-free, OOB write, arbitrary write, or page-cache corruption.
* No privilege escalation or confidentiality signal. The leak does not expose sensitive data or bypass a security boundary.
3. Reachability analysis
The bug is reachable during USB probe of a malformed or incompatible CAIAQ/UAC device. No local software privileges are required once the device is physically attached, but the practical attacker model is physical access or equivalent USB device emulation. Namespaces and containers do not materially lower the requirement because USB device attachment and host driver probing are host-controlled. The path is not network reachable.
4. Severity interpretation
This behaves like a Low-like resource leak issue. The realistic impact is memory/resource consumption if probe failures are repeated. There is no evidence of memory corruption, persistent kernel compromise, privilege escalation, or information disclosure.
5. One-sentence report phrase
A malformed USB audio device can trigger an ALSA caiaq probe-failure path that leaks a `usb_device` reference, causing only resource-exhaustion DoS under repeated physical-device probing.
6. Manual review recommendation
NO MANUAL CHECK NEEDED. This is a physical, driver-specific refcount leak with no supported memory corruption or security-boundary bypass primitive.
======================================================================
UPSTREAM PATCH SUMMARY
======================================================================
Patch: ALSA: caiaq: fix usb_dev refcount leak on probe failure
Commit: 50c6a1f05973f56d23280c9d7645a7a5734e0907
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=50c6a1f05973f56d23280c9d7645a7a5734e0907
Commit description:
create_card() takes a reference on the USB device with usb_get_dev()
and stores the matching usb_put_dev() in card_free(), which is
installed as the snd_card's ->private_free destructor.
However, ->private_free is only assigned near the end of init_card(),
after several failure points (usb_set_interface(), EP type checks,
usb_submit_urb(), the EP1_CMD_GET_DEVICE_INFO exchange, and its
timeout). When any of those fail, init_card() returns an error to
snd_probe(), which calls snd_card_free(card). Because ->private_free
is still NULL, card_free() never runs, the usb_get_dev() reference
is not dropped, and the struct usb_device leaks along with its
descriptor allocations and device_private.
syzbot reproduces this with a malformed UAC3 device whose only valid
altsetting is 0; init_card()'s usb_set_interface(usb_dev, 0, 1) call
fails with -EIO and triggers the leak.
Move the ->private_free assignment into create_card(), immediately
after usb_get_dev(), so that every error path reaching snd_card_free()
balances the reference. card_free()'s callees (snd_usb_caiaq_input_free,
free_urbs, kfree) already tolerate the partially-initialized state
because the chip private area is zero-initialized by snd_card_new().
Fixes: 80bb50e ("ALSA: caiaq: take a reference on the USB device in create_card()")
Reported-by: [email protected]
Closes: https://syzkaller.appspot.com/bug?extid=2afd7e71155c7e241560
Tested-by: [email protected]
Cc: [email protected]
Signed-off-by: Deepanshu Kartikey <[email protected]>
Link: https://patch.msgid.link/[email protected]
Signed-off-by: Takashi Iwai <[email protected]>
Signed-off-by: Greg Kroah-Hartman <[email protected]>
Changed files:
sound/usb/caiaq/device.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=50c6a1f05973f56d23280c9d7645a7a5734e0907
======================================================================
DETAILED REPORT METHODOLOGY
======================================================================
The original Linux kernel CVE announcement for CVE-2026-46048 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-46048
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:L/PR:N/UI:R/S:U/C:N/I:N/A:L
The Best / paranoid CVSS vector: AV:P/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H
The Best / paranoid CVSS score: 4.3
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: 0
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: LOW
KPANIC detected for this report: NO
Published priority for this report (same as in Subject): LOW
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).
reply other threads:[~2026-05-27 19:21 UTC|newest]
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