CVE-2023-52731 – A use-after-free vulnerability in the Linux ker... (How to Fix)

Q: What is the severity of CVE-2023-52731?

CVE-2023-52731 has a CVSS score of 7.8 (HIGH). A use-after-free vulnerability in the Linux kernel's framebuffer (fbdev) subsystem with deferred I/O support allows memory corruption when a framebuffer device is closed while dirty pages remain queued. This can lead to kernel crashes or potential privilege escalation. Affects Linux systems using framebuffer devices with deferred I/O enabled.

📋 TL;DR

A use-after-free vulnerability in the Linux kernel's framebuffer (fbdev) subsystem with deferred I/O support allows memory corruption when a framebuffer device is closed while dirty pages remain queued. This can lead to kernel crashes or potential privilege escalation. Affects Linux systems using framebuffer devices with deferred I/O enabled.

💻 Affected Systems

Products:

Linux kernel

Versions: Kernel versions before the fix commits (specific versions vary by distribution)

Operating Systems: Linux distributions using affected kernel versions

Default Config Vulnerable: ✅ No

Notes: Only vulnerable when framebuffer devices with deferred I/O are used (common in embedded systems, some desktop environments, or systems with specific display configurations).

📦 What is this software?

Linux Kernel by Linux

The Linux Kernel is the core component of the Linux operating system, serving as the critical interface between computer hardware and software processes. As the heart of millions of servers, cloud infrastructure, embedded systems, Android devices, and IoT deployments worldwide, the Linux Kernel mana...

Learn more about Linux Kernel →

Linux Kernel by Linux

The Linux Kernel is the core component of the Linux operating system, serving as the critical interface between computer hardware and software processes. As the heart of millions of servers, cloud infrastructure, embedded systems, Android devices, and IoT deployments worldwide, the Linux Kernel mana...

Learn more about Linux Kernel →

Linux Kernel by Linux

The Linux Kernel is the core component of the Linux operating system, serving as the critical interface between computer hardware and software processes. As the heart of millions of servers, cloud infrastructure, embedded systems, Android devices, and IoT deployments worldwide, the Linux Kernel mana...

Learn more about Linux Kernel →

Linux Kernel by Linux

The Linux Kernel is the core component of the Linux operating system, serving as the critical interface between computer hardware and software processes. As the heart of millions of servers, cloud infrastructure, embedded systems, Android devices, and IoT deployments worldwide, the Linux Kernel mana...

Learn more about Linux Kernel →

Linux Kernel by Linux

The Linux Kernel is the core component of the Linux operating system, serving as the critical interface between computer hardware and software processes. As the heart of millions of servers, cloud infrastructure, embedded systems, Android devices, and IoT deployments worldwide, the Linux Kernel mana...

Learn more about Linux Kernel →

Linux Kernel by Linux

The Linux Kernel is the core component of the Linux operating system, serving as the critical interface between computer hardware and software processes. As the heart of millions of servers, cloud infrastructure, embedded systems, Android devices, and IoT deployments worldwide, the Linux Kernel mana...

Learn more about Linux Kernel →

Linux Kernel by Linux

The Linux Kernel is the core component of the Linux operating system, serving as the critical interface between computer hardware and software processes. As the heart of millions of servers, cloud infrastructure, embedded systems, Android devices, and IoT deployments worldwide, the Linux Kernel mana...

Learn more about Linux Kernel →

Linux Kernel by Linux

The Linux Kernel is the core component of the Linux operating system, serving as the critical interface between computer hardware and software processes. As the heart of millions of servers, cloud infrastructure, embedded systems, Android devices, and IoT deployments worldwide, the Linux Kernel mana...

Learn more about Linux Kernel →

Linux Kernel by Linux

The Linux Kernel is the core component of the Linux operating system, serving as the critical interface between computer hardware and software processes. As the heart of millions of servers, cloud infrastructure, embedded systems, Android devices, and IoT deployments worldwide, the Linux Kernel mana...

Learn more about Linux Kernel →

⚠️ Risk & Real-World Impact

🔴

Worst Case

Kernel panic leading to system crash, or potential local privilege escalation to root if an attacker can trigger the condition and control memory corruption.

🟠

Likely Case

System instability, kernel crashes, or denial of service when framebuffer devices with deferred I/O are opened and closed repeatedly.

🟢

If Mitigated

Minor system instability that requires physical access or local user privileges to trigger.

🌐 Internet-Facing: LOW - Requires local access to framebuffer devices, not directly exploitable over network.

🏢 Internal Only: MEDIUM - Local users or processes with framebuffer access could cause system instability or potentially escalate privileges.

🎯 Exploit Status

Public PoC: ✅ No

Weaponized: UNKNOWN

Unauthenticated Exploit: ✅ No

Complexity: MEDIUM

Requires local access and ability to open/close framebuffer devices. Exploitation would require triggering the specific deferred I/O cleanup race condition.

🛠️ Fix & Mitigation

✅ Official Fix

Patch Version: Kernel versions containing commits: 3efc61d95259956db25347e2a9562c3e54546e20, 87b9802ca824fcee7915e717e9a60471af62e8e9, f1d91f0e9d5a240a809698d7d9c5a538e7dcc149

Vendor Advisory: https://git.kernel.org/stable/c/3efc61d95259956db25347e2a9562c3e54546e20

Restart Required: Yes

Instructions:

1. Update Linux kernel to version containing the fix commits. 2. Check distribution-specific security advisories. 3. Reboot system after kernel update.

🔧 Temporary Workarounds

Disable framebuffer deferred I/O

linux

Prevent use of framebuffer devices with deferred I/O feature

echo 0 > /sys/class/graphics/fb*/deferred_io
Remove 'fbcon=map:1' or similar framebuffer options from kernel command line

🧯 If You Can't Patch

Restrict access to framebuffer devices (/dev/fb*) to trusted users only
Monitor system logs for kernel crashes or Oops messages related to fbdev

🔍 How to Verify

Check if Vulnerable:

Check kernel version and if framebuffer devices exist: ls -la /dev/fb* && uname -r

Check Version:

uname -r

Verify Fix Applied:

Verify kernel version includes fix commits: git log --oneline | grep -E '3efc61d|87b9802|f1d91f0'

📡 Detection & Monitoring

Log Indicators:

Kernel Oops messages mentioning fbdev, deferred_io, or pageref
System crashes when closing framebuffer applications

Network Indicators:

None - local vulnerability only

SIEM Query:

source="kernel" AND ("fbdev" OR "deferred_io" OR "pageref" OR "Oops")

📊 Metadata

CVE ID: CVE-2023-52731

CVSS v3 Score: 7.8 (HIGH)

CVSS Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

CWE: CWE-125

Published: May 21, 2024

Last Updated: September 23, 2025

🔗 References

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🔗 Related Vulnerabilities

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