[CVE-2026-68184][MODERATE REGULAR] cdrom: fix stack out-of-bounds read in CDROMVOLCTRL

[CVE-2026-68184][MODERATE REGULAR] cdrom: fix stack out-of-bounds read in CDROMVOLCTRL

[AL-KERNEL]

CVE: CVE-2026-68184
Priority: MODERATE REGULAR
AL-KERNEL base severity: MODERATE
KPANIC flag: NO
Patch: cdrom: fix stack out-of-bounds read in CDROMVOLCTRL
Commit: 7344c84e32413e5c8832f74b8a612b0194e5c051
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=7344c84e32413e5c8832f74b8a612b0194e5c051
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-68184
Analysis date: Mon, 10 Aug 2026 16:55:44 -0400
ActionableScore: 3
ActionableScore lower bound: 2
Actionable bucket: Ordinary Moderate / Low-like with manual-review sensitivity for kernel stack disclosure
Manual review required: NO

Summary:
A stack out-of-bounds read in CDROMVOLCTRL can send a small amount of adjacent kernel stack data to a CD-ROM device when a non-zero block descriptor causes cgc buffer to be advanced without reducing cgc buflen.

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

The original Linux kernel CVE announcement for CVE-2026-68184 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-68184

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 REGULAR
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-2026-68184	MODERATE	CHECK WITH IMPACT FROM ORIG NN LOW	Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:L/AC:H/PR:L/UI:N/S:U/C:L/I:N/A:L';CWE-126;CWE-125;*CWE-200;Other CVSS 'AV:L/AC:H/PR:L/UI:N/S:U/C:L/I:N/A:N';BEST CVSS score: '3.6';DESCR 'A stack out-of-bounds read in the CDROMVOLCTRL path can occur because mmc_ioctl_cdrom_volume moves cgc buffer forward to build a MODE SELECT payload but does not reduce cgc buflen by the same amount. When a drive reports a non-zero block descriptor length, cdrom_mode_select may read beyond the 32 byte stack buffer and send extra kernel stack bytes to the CDROM device as part of the outgoing payload. For the CVSS the PR:L is used because a local user or process needs access to the cdrom ioctl path and a suitable device condition is required. The issue is not network reachable. Impact is mainly limited confidentiality exposure to the device side, with only low availability impact in hardened or debug configurations.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Ordinary Moderate / Low-like with manual-review sensitivity for kernel stack disclosure (with actual score 3)	YES	WRITE OOB HARDWARE PACKET  DECREASED_TO_MODERATE_REGULAR_FROM_MODERATE7_BASED_ON_GUESSCVSS	NO	NO	checked

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

ActionableScore=3
ActionableScoreLower=2

## 1. ActionableScore

* Conservative score: 2
* Paranoid score: 3
* Final recommended bucket: **Ordinary Moderate / Low-like with manual-review sensitivity for kernel stack disclosure**::

## 2. Signal breakdown

Conservative signals:

* Local unprivileged or low-privileged trigger: +1
  A local process with access to the CD-ROM device ioctl path can call CDROMVOLCTRL.
* Firmware-mediated external influence: +1
  The bug depends on a drive reporting a non-zero block descriptor length, and the overread bytes are sent back to the device as MODE SELECT payload.
* Confidentiality impact plausible: +1
  The primitive is a small stack out-of-bounds read, potentially exposing adjacent kernel stack bytes to the device side.
* Rare or difficult-to-reach hardware condition: -1
  It requires a CD-ROM style device path and a device behavior that returns a block descriptor for this mode page.

Paranoid adjustment:

* Availability impact low but possible: +1
  In hardened or debug configurations, stack OOB reads or abnormal packet payloads could produce warnings or failures, but this is not the main demonstrated impact.

Not counted:

* No generic strong memory corruption. This is a read past a stack buffer, not an OOB write, UAF, double free, type confusion, or arbitrary write.
* No privilege escalation signal. The patch does not show attacker-controlled overwrite, reclaim, callback control, or object confusion.
* No network reachability. The affected path is a local CD-ROM ioctl path.

## 3. Reachability analysis

The realistic trigger is local access to a CD-ROM block device and the CDROMVOLCTRL ioctl path. In normal desktop or server deployments this usually depends on device-node permissions, group membership, udev policy, or a process already allowed to access optical media devices. Containers normally do not receive direct access to such device nodes unless explicitly passed through.

The device behavior matters. The issue is only triggered when the drive returns a non-zero block descriptor length, and the leaked bytes are sent as extra MODE SELECT payload to the device. This makes a malicious or observable virtual or physical device more relevant than a pure local-only attacker who cannot inspect device-side traffic.

## 4. Severity interpretation

This behaves like a low-end Moderate information disclosure bug, not an Important kernel memory corruption issue. The theoretical concern is kernel stack disclosure, but the amount appears small and the disclosure sink is the CD-ROM device side, not directly normal userspace. There is no evidence of write corruption, LPE, persistent damage, or remote attack surface.

The paranoid score is raised only to preserve manual-review sensitivity for kernel stack OOB reads, especially where a virtual or malicious device could observe the MODE SELECT payload.

## 5. One-sentence report phrase

A stack out-of-bounds read in CDROMVOLCTRL can send a small amount of adjacent kernel stack data to a CD-ROM device when a non-zero block descriptor causes cgc buffer to be advanced without reducing cgc buflen.

## 6. Manual review recommendation

MANUAL CHECK RECOMMENDED

Manual review is recommended because this is a kernel stack out-of-bounds read with a plausible information disclosure path to the device side. It should not be treated as Important without additional evidence of a broader disclosure primitive, attacker-visible readback, memory corruption, or privilege escalation.

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

Patch: cdrom: fix stack out-of-bounds read in CDROMVOLCTRL
Commit: 7344c84e32413e5c8832f74b8a612b0194e5c051
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=7344c84e32413e5c8832f74b8a612b0194e5c051

Commit description:

mmc_ioctl_cdrom_volume() first reads the audio control mode page into a
32-byte stack buffer with cgc->buflen set to 24.  If the device reports a
block descriptor, the function increases cgc->buflen to include that
descriptor and reads the page again.

For CDROMVOLCTRL, the function then builds a MODE SELECT parameter list
by moving cgc->buffer forward by offset - 8 bytes.  This drops the block
descriptor from the outgoing payload and leaves a new 8-byte mode
parameter header in front of the audio control page.  However, cgc->buflen
is left unchanged.

With a standard 8-byte block descriptor, cgc->buffer points at buffer + 8
but cgc->buflen remains 32.  cdrom_mode_select() therefore asks the low
level packet path to write 32 bytes from that adjusted pointer, reading 8
bytes past the end of the 32-byte stack buffer.

This is not hit by CDROMVOLREAD, and CDROMVOLCTRL only triggers it on
drives that return a non-zero block descriptor length, which helps explain
why it has gone unnoticed.  The overread is also sent to the device as
extra MODE SELECT payload, so it may not produce an obvious local failure.

Reduce cgc->buflen by the same amount as the buffer pointer adjustment so
the MODE SELECT transfer covers only the intended parameter list.

Fixes: 1da177e ("Linux-2.6.12-rc2")
Cc: stable@vger.kernel.org
Signed-off-by: Xu Rao <raoxu@uniontech.com>
Signed-off-by: Phillip Potter <phil@philpotter.co.uk>
Link: https://patch.msgid.link/20260720194421.1497-2-phil@philpotter.co.uk
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Changed files:
  drivers/cdrom/cdrom.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=7344c84e32413e5c8832f74b8a612b0194e5c051

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

The original Linux kernel CVE announcement for CVE-2026-68184 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-68184

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:L/UI:N/S:U/C:L/I:N/A:N
  The Best / paranoid CVSS vector: AV:L/AC:H/PR:L/UI:N/S:U/C:L/I:N/A:L
  The Best / paranoid CVSS score: 3.6

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: 2
  Paranoid ActionableScore: 3

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 REGULAR

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).