From: AL-KERNEL <[email protected]>
To: [email protected]
Subject: [CVE-2026-74680][LOW] usb: atm: cxacru: properly kill rcv_urb on error in cxacru_cm()
Date: Sat, 22 Aug 2026 15:03:05 -0400 [thread overview]
Message-ID: <[email protected]> (raw)
CVE: CVE-2026-74680
Priority: LOW
AL-KERNEL base severity: LOW
KPANIC flag: NO
Patch: usb: atm: cxacru: properly kill rcv_urb on error in cxacru_cm()
Commit: 6133b461058316e3ccba7331f974d110d4c08b23
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=6133b461058316e3ccba7331f974d110d4c08b23
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-74680
Analysis date: Sat, 22 Aug 2026 15:03:05 -0400
ActionableScore: 2
ActionableScore lower bound: 1
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-2026-74680 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-74680
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-2026-74680 LOW CHECK WITH IMPACT FROM ORIG NN LOW Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:P/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H';CWE-703;CWE-459;*CWE-664;Other CVSS 'AV:P/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L';BEST CVSS score: '4.6';DESCR 'cxacru_cm can return on an error path without killing an already submitted rcv_urb, leaving the receive URB active after a failed control message. A later call to cxacru_cm can try to submit the same active URB again and trigger a usb_submit_urb warning. For the CVSS the PR:N value is used because a malicious or faulty attached USB device can trigger the condition without privileges on the victim, but the attack requires physical or USB device level access rather than network reachability. The issue is not network reachable. Impact is denial of service or driver malfunction, with high availability only in the paranoid case where warnings are treated as fatal or the device path repeatedly wedges the system.';NO MANUAL CHECK; ,and ActionableScore result is Ordinary Moderate / Low-like (with actual score 2) YES USB WARNONLY ERRORPATH IMPROVEONLY LINUS SYZBOT NO NO checked
======================================================================
ACTIONABLESCORE ANALYSIS
======================================================================
ActionableScore=2
ActionableScoreLower=1
1. ActionableScore
* Conservative score: 1
* Paranoid score: 2
* Final recommended bucket: **Ordinary Moderate / Low-like**::
2. Signal breakdown
* Firmware-mediated or device-mediated external influence: +1. A faulty or malicious attached USB ATM device can influence the error path, but this is not network reachable.
* Real lifetime or async state mismatch: +1. The bug leaves rcv_urb active after cxacru_cm() exits on error, creating an invalid URB lifecycle state.
* Availability impact realistic: +1 in the conservative interpretation only as driver malfunction or warning-level DoS.
* Reliable kernel crash / strong DoS: +1 only in the paranoid interpretation, mainly if panic_on_warn is enabled or repeated device initialization wedges the system.
* Physical-only or rare hardware-only condition: -2. Triggering requires a cxacru USB ATM device path or USB-level emulation.
* No generic memory corruption bonus. The patch shows active URB resubmission warning, not UAF, double-free, OOB write, type confusion, or controlled overwrite.
* No privilege escalation signal. There is no supported reclaim, stale callback control, arbitrary write, or object replacement primitive.
3. Reachability analysis
The likely trigger is a faulty or malicious USB device, or a local test environment able to emulate such a device. No local user privileges are needed once the malicious physical device is attached, so the CVSS-style PR:N interpretation is reasonable for the physical attack model. The path is not remotely network reachable. The affected driver is hardware-specific and not a broad default-exposed subsystem. Namespaces and containers do not materially reduce the physical USB requirement.
Call-site confidence: high, because the commit message includes the relevant call chain through cxacru_atm_start(), cxacru_poll_status(), and cxacru_cm().
4. Severity interpretation
This behaves like a Low or ordinary Moderate reliability issue, not an Important-class vulnerability. The demonstrated impact is an active URB resubmission warning and possible driver or kernel availability impact in stricter configurations. Theoretical memory corruption is not supported by the patch context, and realistic exploitation evidence points to DoS only.
5. One-sentence report phrase
cxacru_cm() could leave rcv_urb active on an error path, allowing a later cxacru_cm() call to resubmit an already active URB and trigger a USB core warning or DoS through a physical or emulated USB ATM device.
6. Manual review recommendation
NO MANUAL CHECK NEEDED
The issue is physical-device scoped, hardware-specific, and supported impact is warning-level DoS or driver malfunction only, with no concrete memory corruption or privilege escalation primitive.
======================================================================
UPSTREAM PATCH SUMMARY
======================================================================
Patch: usb: atm: cxacru: properly kill rcv_urb on error in cxacru_cm()
Commit: 6133b461058316e3ccba7331f974d110d4c08b23
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=6133b461058316e3ccba7331f974d110d4c08b23
Commit description:
If cxacru_cm() encounters an error while submitting or waiting for snd_urb,
it aborts and returns the error without killing the already submitted
rcv_urb. This leaves the rcv_urb active.
When this happens during initialization (e.g., in cxacru_atm_start()), the
driver may ignore the error and proceed to call cxacru_poll_status(), which
invokes cxacru_cm() again. Attempting to submit the still-active rcv_urb
triggers a warning in usb_submit_urb():
cxacru 1-1:1.0: send of cm 0x84 failed (-104)
ATM dev 0: cxacru_atm_start: CHIP_ADSL_LINE_START returned -104
------------[ cut here ]------------
URB ffff88812658d200 submitted while active
WARNING: drivers/usb/core/urb.c:379 at usb_submit_urb+0x79/0x18b0
drivers/usb/core/urb.c:379
...
Call Trace:
<TASK>
cxacru_cm+0x21a/0xf10 drivers/usb/atm/cxacru.c:631
cxacru_cm_get_array drivers/usb/atm/cxacru.c:722 [inline]
cxacru_poll_status+0x178/0x1110 drivers/usb/atm/cxacru.c:828
cxacru_atm_start+0x185/0x360 drivers/usb/atm/cxacru.c:814
usbatm_atm_init+0x144/0x3a0 drivers/usb/atm/usbatm.c:927
usbatm_usb_probe+0x15cb/0x1db0 drivers/usb/atm/usbatm.c:1178
cxacru_usb_probe+0x17f/0x220 drivers/usb/atm/cxacru.c:1370
...
To fix this, ensure that rcv_urb is properly killed if cxacru_cm() aborts
early. We can safely call usb_kill_urb() on rcv_urb in the error path, as
it is safe to call even if the URB is not active (e.g., if it failed to
submit in the first place, or if it already completed).
Fixes: 1b0e614 ("[PATCH] USB ATM: driver for the Conexant AccessRunner chipset cxacru")
Cc: stable <[email protected]>
Assisted-by: Gemini:gemini-3.5-flash Gemini:gemini-3.1-pro-preview syzbot
Reported-by: [email protected]
Closes: https://syzkaller.appspot.com/bug?extid=c9dff578c3a41775176a
Link: https://syzkaller.appspot.com/ai_job?id=75fec6f2-c8a6-43b1-b184-4d26baba86cc
Signed-off-by: Aleksandr Nogikh <[email protected]>
Link: https://patch.msgid.link/[email protected]
Signed-off-by: Greg Kroah-Hartman <[email protected]>
Signed-off-by: Greg Kroah-Hartman <[email protected]>
Changed files:
drivers/usb/core/urb.c:379
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=6133b461058316e3ccba7331f974d110d4c08b23
======================================================================
DETAILED REPORT METHODOLOGY
======================================================================
The original Linux kernel CVE announcement for CVE-2026-74680 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-74680
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:N/S:U/C:N/I:N/A:L
The Best / paranoid CVSS vector: AV:P/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
The Best / paranoid CVSS score: 4.6
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: 1
Paranoid ActionableScore: 2
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:[~2026-08-22 19:03 UTC|newest]
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