CVE-2023-52973 – This is a use-after-free vulnerability in the L... (How to Fix)

Q: What is the severity of CVE-2023-52973?

CVE-2023-52973 has a CVSS score of 7.8 (HIGH). This is a use-after-free vulnerability in the Linux kernel's virtual console screen driver (vc_screen). It allows attackers with local access to potentially execute arbitrary code or cause kernel crashes by exploiting a race condition between vcs_read() and vc_deallocate(). All Linux systems using affected kernel versions are vulnerable.

📋 TL;DR

This is a use-after-free vulnerability in the Linux kernel's virtual console screen driver (vc_screen). It allows attackers with local access to potentially execute arbitrary code or cause kernel crashes by exploiting a race condition between vcs_read() and vc_deallocate(). All Linux systems using affected kernel versions are vulnerable.

💻 Affected Systems

Products:

Linux kernel

Versions: Kernel versions before the fix commits (specific versions vary by distribution, generally 6.2.0-rc5 and earlier affected)

Operating Systems: All Linux distributions using vulnerable kernel versions

Default Config Vulnerable: ⚠️ Yes

Notes: Requires CONFIG_VT and CONFIG_VT_CONSOLE enabled (common in most desktop/server configurations). Virtual console access needed to trigger.

📦 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 →

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

Local privilege escalation to root, kernel panic causing system crash, or arbitrary code execution in kernel context leading to complete system compromise.

🟠

Likely Case

Kernel crash leading to denial of service, or local privilege escalation if combined with other vulnerabilities.

🟢

If Mitigated

Limited to denial of service if kernel hardening features like KASAN or SLAB_FREELIST_HARDENED are enabled.

🌐 Internet-Facing: LOW - Requires local access to exploit, not directly reachable via network.

🏢 Internal Only: MEDIUM - Local users or compromised accounts could exploit this for privilege escalation or DoS attacks.

🎯 Exploit Status

Public PoC: ✅ No

Weaponized: UNKNOWN

Unauthenticated Exploit: ✅ No

Complexity: MEDIUM

Requires local access and race condition triggering. Syzkaller fuzzer discovered this, suggesting exploitability but no public exploits known.

🛠️ Fix & Mitigation

✅ Official Fix

Patch Version: Fixed in kernel commits: 226fae124b2dac217ea5436060d623ff3385bc34, 55515d7d8743b71b80bfe68e89eb9d92630626ab, 6332f52f44b9776568bf3c0b714ddfb0bb175e78, 8506f16aae9daf354e3732bcfd447e2a97f023df, af79ea9a2443016f64d8fd8d72020cc874f0e066

Vendor Advisory: https://git.kernel.org/stable/c/226fae124b2dac217ea5436060d623ff3385bc34

Restart Required: Yes

Instructions:

1. Update Linux kernel to patched version from your distribution. 2. For RHEL/CentOS: yum update kernel. 3. For Ubuntu/Debian: apt update && apt upgrade linux-image-*. 4. Reboot system to load new kernel.

🔧 Temporary Workarounds

Disable virtual consoles

all

Remove virtual console access by disabling VT subsystem (not practical for most systems)

echo 'blacklist vt' > /etc/modprobe.d/blacklist-vt.conf
update-initramfs -u

🧯 If You Can't Patch

Restrict access to /dev/vcs* devices using filesystem permissions
Implement strict user privilege separation and limit local user access

🔍 How to Verify

Check if Vulnerable:

Check kernel version: uname -r and compare with distribution's patched versions. Check if /dev/vcs devices exist.

Check Version:

uname -r

Verify Fix Applied:

Verify kernel version after update matches patched version from vendor. Check git commit hash if building from source.

📡 Detection & Monitoring

Log Indicators:

Kernel panic logs
KASAN use-after-free reports in dmesg
OOM killer activity related to vt processes

Network Indicators:

None - local exploit only

SIEM Query:

source="kernel" AND ("KASAN: use-after-free" OR "BUG: KASAN" OR "vc_screen" OR "vcs_read")

📊 Metadata

CVE ID: CVE-2023-52973

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-416

EPSS Score: 0.04% exploit probability (13.1th percentile)

Published: March 27, 2025

Last Updated: April 1, 2025

🔗 References

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🔗 Related Vulnerabilities

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