[CVE-2026-63964][LOW] usb: typec: ucsi: ccg: reject firmware images without a ':' record header

[CVE-2026-63964][LOW] usb: typec: ucsi: ccg: reject firmware images without a ':' record header

[AL-KERNEL]

CVE: CVE-2026-63964
Priority: LOW
AL-KERNEL base severity: LOW
KPANIC flag: NO
Patch: usb: typec: ucsi: ccg: reject firmware images without a ':' record header
Commit: b41dfc033fe594e152648050e95b9489cd53e9e3
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=b41dfc033fe594e152648050e95b9489cd53e9e3
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-63964
Analysis date: Sun, 19 Jul 2026 13:56:53 -0400
ActionableScore: 2
ActionableScore lower bound: 0
Actionable bucket: Ordinary Moderate / Low-like
Manual review required: NO

Summary:
A malformed CCG firmware image without a colon record header can trigger an invalid kernel read in `do_flash()`, causing a local privileged kernel crash, but exploitation normally requires administrative firmware update control and does not show an LPE primitive.

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ABOUT THIS REPORT
======================================================================

The original Linux kernel CVE announcement for CVE-2026-63964 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-63964

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-2026-63964	LOW	CHECK WITH IMPACT FROM ORIG NN LOW	Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H';CWE-690;**CWE-476;*CWE-20;Other CVSS 'AV:L/AC:L/PR:H/UI:N/S:U/C:N/I:N/A:H';BEST CVSS score: '5.5';DESCR 'A malformed CCG firmware image without a colon record header can make do_flash continue after strnchr returns NULL. The next search uses p plus 1 near address 1 with a very large length, which can trigger an invalid kernel read and an oops or kernel crash. For the CVSS the PR:L paranoid interpretation is used only when firmware update control is delegated to a less privileged local service account or operator. In default deployments PR:H is more realistic because placing a crafted file under /lib/firmware and writing the do_flash sysfs attribute normally requires administrator privileges. The issue is local only and is not network reachable. Impact is denial of service via kernel crash, with no supported UAF, OOB write, information leak, or privilege escalation primitive.';NO MANUAL CHECK; ,and ActionableScore result is Ordinary Moderate / Low-like (with actual score 1)	YES	DANGER USB ERRORPATH  DECREASED_TO_MODERATE_REGULAR_FROM_MODERATE7_BASED_ON_GUESSCVSS_AND_CIANNH DECREASED_TO_LOW_FROM_MODERATE_BASED_ON_ACTIONABLESCORELESSTHAN3	NO	NO	checked

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ACTIONABLESCORE ANALYSIS
======================================================================

ActionableScore=2
ActionableScoreLower=0

## 1. ActionableScore

* Conservative score: 0
* Paranoid score: 2
* Final recommended bucket: **Ordinary Moderate / Low-like**

## 2. Signal breakdown

Conservative scoring:

* Reliable kernel crash / strong DoS: +1. The commit explicitly states that a crafted firmware image without a colon record header can cause an invalid `strnchr()` call from near address `1` with a huge length, resulting in an oops or crash.
* Requires admin/root in typical deployments: -2. The described trigger requires placing a crafted blob under `/lib/firmware` and writing the `do_flash` sysfs attribute, which normally requires root or equivalent administrative control.
* Rare and difficult-to-reach subsystem/configuration: -1. This is specific to the USB Type-C UCSI CCG firmware flashing path and requires suitable hardware plus an explicit firmware update action.
* Weak corruption only: +0. This is an invalid pointer dereference / invalid kernel read leading to crash. The patch does not show UAF, double free, OOB write, arbitrary write, type confusion, refcount abuse, or attacker-controlled object reuse.

Paranoid scoring:

* Reliable kernel crash / strong DoS: +1.
* Firmware-fed parser / firmware update influence: +1. The crashing input is a malformed firmware image processed by a privileged kernel device-management path.
* No root penalty in the paranoid variant only if firmware update is delegated to a reduced-privilege local service account or operator. This is not the normal deployment assumption.

No score is added for privilege escalation, confidentiality, or integrity because the demonstrated primitive is an invalid read / NULL-derived pointer dereference causing oops, not memory corruption with attacker-controlled reuse or write capability.

## 3. Reachability analysis

A typical attacker needs local administrative ability to install or control the firmware blob and trigger the `do_flash` sysfs operation. This is not network reachable. Namespaces and containers do not normally reduce the privilege requirement because firmware installation and device sysfs flashing controls are host-level operations. A paranoid PR:L interpretation is only defensible if a product delegates firmware update operations to a less privileged local service or operator account.

The path is not default-exercised during normal USB Type-C operation. It requires the CCG driver, compatible hardware, firmware update flow, and a malformed firmware image.

Call-site confidence: high. The commit directly describes the failing call path and the patch adds validation immediately before the vulnerable loop.

## 4. Severity interpretation

This behaves like an ordinary Moderate / Low-like privileged local DoS. The realistic impact is a kernel oops or crash during a malformed firmware update attempt. There is no evidence of a practical privilege escalation path. The theoretical concern is limited to invalid kernel memory read during string scanning, but the patch and commit do not support UAF, write corruption, object replacement, or information disclosure.

## 5. One-sentence report phrase

A malformed CCG firmware image without a colon record header can trigger an invalid kernel read in `do_flash()`, causing a local privileged kernel crash, but exploitation normally requires administrative firmware update control and does not show an LPE primitive.

## 6. Manual review recommendation

NO MANUAL CHECK NEEDED

This can be auto-closed in most triage workflows because it is a rare hardware-specific, local privileged firmware update DoS with no supported memory corruption or privilege escalation primitive.

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

Patch: usb: typec: ucsi: ccg: reject firmware images without a ':' record header
Commit: b41dfc033fe594e152648050e95b9489cd53e9e3
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=b41dfc033fe594e152648050e95b9489cd53e9e3

Commit description:

do_flash() locates the first .cyacd record with

	p = strnchr(fw->data, fw->size, ':');
	while (p < eof) {
		s = strnchr(p + 1, eof - p - 1, ':');
		...
	}

If the firmware image contains no ':' byte,  strnchr() returns NULL.
NULL compares less than the valid kernel pointer eof, so the loop body
runs and strnchr() is called with p + 1 == (void *)1 and a length of
roughly (unsigned long)eof, causing a wonderful crash.

The not_signed_fw fallthrough earlier in do_flash() and the chip-state
branches in ccg_fw_update_needed() allow an unsigned blob to reach this
loop, so a root user who can place a crafted file under /lib/firmware
and write the do_flash sysfs attribute can trigger the oops.

Bail out with -EINVAL when the initial strnchr() returns NULL.

Assisted-by: gkh_clanker_t1000
Cc: stable <stable@kernel.org>
Cc: Heikki Krogerus <heikki.krogerus@linux.intel.com>
Reviewed-by: Heikki Krogerus <heikki.krogerus@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Link: https://patch.msgid.link/2026051405-posture-shrill-7884@gregkh
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Changed files:
  drivers/usb/typec/ucsi/ucsi_ccg.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=b41dfc033fe594e152648050e95b9489cd53e9e3

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

The original Linux kernel CVE announcement for CVE-2026-63964 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-63964

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:L/PR:H/UI:N/S:U/C:N/I:N/A:H
  The Best / paranoid CVSS vector: AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
  The Best / paranoid CVSS score: 5.5

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: 0
  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 alexanjelausa@gmail.com (and both
send reply to CVE record itself too and see "reply" button below for howto reply).