CVE-2023-2235 – A use-after-free vulnerability in the Linux ker... (How to Fix)

Q: What is the severity of CVE-2023-2235?

CVE-2023-2235 has a CVSS score of 7.8 (HIGH). A use-after-free vulnerability in the Linux kernel's Performance Events (perf) subsystem allows local attackers to escalate privileges from an unprivileged user to root. This affects Linux systems with the perf subsystem enabled. Attackers need local access to exploit this vulnerability.

📋 TL;DR

A use-after-free vulnerability in the Linux kernel's Performance Events (perf) subsystem allows local attackers to escalate privileges from an unprivileged user to root. This affects Linux systems with the perf subsystem enabled. Attackers need local access to exploit this vulnerability.

💻 Affected Systems

Products:

Linux Kernel

Versions: Versions before commit fd0815f632c24878e325821943edccc7fde947a2 (March 2023)

Operating Systems: Linux distributions using vulnerable kernel versions

Default Config Vulnerable: ⚠️ Yes

Notes: Requires CONFIG_PERF_EVENTS kernel configuration enabled (default in most distributions).

📦 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 →

⚠️ Risk & Real-World Impact

🔴

Worst Case

Full root privilege escalation leading to complete system compromise, data theft, persistence establishment, and lateral movement.

🟠

Likely Case

Local privilege escalation allowing attackers to gain root access on affected systems.

🟢

If Mitigated

Limited impact if proper access controls restrict local user accounts and kernel hardening measures are in place.

🌐 Internet-Facing: LOW - Requires local access to exploit, cannot be triggered remotely.

🏢 Internal Only: HIGH - Any local user account can potentially exploit this to gain root privileges.

🎯 Exploit Status

Public PoC: ⚠️ Yes

Weaponized: LIKELY

Unauthenticated Exploit: ✅ No

Complexity: MEDIUM

Exploitation requires local access and knowledge of kernel exploitation techniques. Proof-of-concept code has been published.

🛠️ Fix & Mitigation

✅ Official Fix

Patch Version: Kernel versions including commit fd0815f632c24878e325821943edccc7fde947a2

Vendor Advisory: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=fd0815f632c24878e325821943edccc7fde947a2

Restart Required: Yes

Instructions:

1. Update Linux kernel to version containing the fix. 2. For distributions: Use package manager (apt/yum/dnf) to update kernel package. 3. Reboot system to load new kernel.

🔧 Temporary Workarounds

Disable perf subsystem

linux

Disable the Performance Events subsystem to prevent exploitation

echo 0 > /proc/sys/kernel/perf_event_paranoid
sysctl -w kernel.perf_event_paranoid=3

Restrict perf usage

linux

Limit which users can use perf events

sysctl -w kernel.perf_event_paranoid=2

🧯 If You Can't Patch

Implement strict access controls to limit local user accounts
Monitor for privilege escalation attempts and unusual root activity

🔍 How to Verify

Check if Vulnerable:

Check kernel version and if commit fd0815f632c24878e325821943edccc7fde947a2 is present: uname -r && git log --oneline | grep fd0815f632c24878e325821943edccc7fde947a2

Check Version:

uname -r

Verify Fix Applied:

Verify kernel version is updated and contains the fix commit

📡 Detection & Monitoring

Log Indicators:

Kernel panic logs
OOM killer activity
Unusual privilege escalation in audit logs

Network Indicators:

None - local exploit only

SIEM Query:

search 'kernel panic' OR 'use-after-free' OR 'privilege escalation' in system logs

📊 Metadata

CVE ID: CVE-2023-2235

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

Published: May 1, 2023

Last Updated: November 21, 2024

🔗 References

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🔗 Related Vulnerabilities

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