Cloudanix VulnDB

CVE-2026-68184

None

CVSS

—

EPSS

0.2%

Published

Aug 10, 2026

CISA due date

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Cloudanix analysis

Schedule a fix SSVC: Track

A bug in how Linux handles certain CD-ROM control commands can let someone already on the machine read a small amount of hidden memory or cause crashes.

Exploitation
Local Privilege
Attacker needs
Local User
Complexity
Low
Impact
Data Exposure
Component
OS kernel
Class
Memory Corruption
Remediation
Upgrade
Effort
Medium
Patch risk
Low

What it actually does

Stack out-of-bounds read in mmc_ioctl_cdrom_volume() for CDROMVOLCTRL ioctls when drives return an 8-byte block descriptor: buffer pointer is advanced but cgc->buflen is not reduced, causing cdrom_mode_select() to read 8 bytes past the 32-byte stack buffer and transmit the excess as MODE SELECT payload.

Why it matters to the business

Local memory disclosure or kernel instability on Linux systems exposing CD-ROM devices; low exploitability reduces immediate risk but still requires patching to maintain kernel integrity across fleets.

How an attack unfolds

A local attacker issues a CDROMVOLCTRL ioctl against a CD-ROM device whose mode sense response includes a block descriptor; the kernel's unadjusted length calculation triggers an 8-byte overread from the stack buffer, sending the leaked bytes to the drive.

How to fix it

Apply the upstream kernel patch that subtracts the offset adjustment from cgc->buflen before the MODE SELECT call; rebuild and deploy updated kernels to all affected systems.

How to confirm the fix worked

Confirm the fix by inspecting cdrom.c for the buflen reduction logic after the buffer pointer adjustment; test with a drive that returns an 8-byte block descriptor and verify no excess bytes are sent.

Typical attack path

  1. Obtain local unprivileged access on a Linux host
  2. Locate a CD-ROM block device that returns a non-zero block descriptor length
  3. Issue CDROMVOLCTRL ioctl with crafted cgc structure
  4. Observe overread behavior or resulting kernel memory exposure

How to detect it

Review kernel audit logs or ftrace for CDROMVOLCTRL ioctls on optical devices; watch for unexpected MODE SELECT transfers or stack-related oops reports referencing cdrom_mode_select.

What your security team should do

  • Prioritize kernel updates on any systems still exposing optical drives
  • Audit local ioctl permissions and consider device node restrictions where CD-ROM functionality is unnecessary
  • Monitor kernel update channels for backports of this fix

The record

In the Linux kernel, the following vulnerability has been resolved: cdrom: fix stack out-of-bounds read in CDROMVOLCTRL 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.

Affected packages

Ecosystem Package Introduced Fixed