CVE-2023-1249 – A use-after-free vulnerability in the Linux ker... (How to Fix)

Q: What is the severity of CVE-2023-1249?

CVE-2023-1249 has a CVSS score of 5.5 (MEDIUM). A use-after-free vulnerability in the Linux kernel's core dump subsystem allows local users to crash the system by triggering a kernel panic. This affects Linux systems that haven't applied the specific kernel patch addressing this memory management flaw.

📋 TL;DR

A use-after-free vulnerability in the Linux kernel's core dump subsystem allows local users to crash the system by triggering a kernel panic. This affects Linux systems that haven't applied the specific kernel patch addressing this memory management flaw.

💻 Affected Systems

Products:

Linux Kernel

Versions: Versions before patch 390031c94211 ('coredump: Use the vma snapshot in fill_files_note')

Operating Systems: Linux distributions using vulnerable kernel versions

Default Config Vulnerable: ⚠️ Yes

Notes: Only affects systems where the specific patch hasn't been applied. CentOS Stream 9 specifically mentioned as missing this fix.

📦 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 →

⚠️ Risk & Real-World Impact

🔴

Worst Case

Local denial of service causing system crash/kernel panic, potentially leading to data corruption or service disruption.

🟠

Likely Case

Local user triggers kernel panic causing system reboot and temporary service interruption.

🟢

If Mitigated

No impact if patch is applied; system remains stable even with malicious local users.

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

🏢 Internal Only: MEDIUM - Local users (including compromised accounts) can crash the system, but requires existing access.

🎯 Exploit Status

Public PoC: ✅ No

Weaponized: UNKNOWN

Unauthenticated Exploit: ✅ No

Complexity: MEDIUM

Requires local user access and knowledge of triggering the use-after-free condition in core dump handling.

🛠️ Fix & Mitigation

✅ Official Fix

Patch Version: Kernel versions with patch 390031c94211 applied

Vendor Advisory: https://patchwork.kernel.org/project/linux-fsdevel/patch/87iltzn3nd.fsf_-_%40email.froward.int.ebiederm.org/

Restart Required: Yes

Instructions:

1. Check current kernel version. 2. Update kernel through distribution's package manager. 3. Reboot system to load patched kernel.

🔧 Temporary Workarounds

Disable core dumps

linux

Prevents the vulnerable core dump functionality from being triggered

ulimit -c 0
echo 'kernel.core_pattern = |/bin/false' >> /etc/sysctl.conf
sysctl -p

🧯 If You Can't Patch

Restrict local user access to minimize attack surface
Implement strict privilege separation and limit user capabilities

🔍 How to Verify

Check if Vulnerable:

Check if kernel version includes patch 390031c94211: grep -q '390031c94211' /proc/version || echo 'Potentially vulnerable'

Check Version:

uname -r

Verify Fix Applied:

Verify kernel version after update and ensure patch is present in kernel source or running version

📡 Detection & Monitoring

Log Indicators:

Kernel panic messages in /var/log/messages or dmesg
Unexpected system reboots
Core dump related errors

Network Indicators:

None - local exploit only

SIEM Query:

source="kernel" AND ("panic" OR "Oops" OR "use-after-free") AND process="coredump"

📊 Metadata

CVE ID: CVE-2023-1249

CVSS v3 Score: 5.5 (MEDIUM)

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

CWE: CWE-416

Published: March 23, 2023

Last Updated: March 19, 2025

🔗 References

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🔗 Related Vulnerabilities

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