CVE-2023-52803 – This is a use-after-free vulnerability in the L... (How to Fix)

Q: What is the severity of CVE-2023-52803?

CVE-2023-52803 has a CVSS score of 5.5 (MEDIUM). This is a use-after-free vulnerability in the Linux kernel's SUNRPC client that occurs when cleaning up pipefs dentries. It allows attackers to potentially cause kernel crashes or execute arbitrary code with kernel privileges. Systems running affected Linux kernel versions with SUNRPC enabled are vulnerable.

📋 TL;DR

This is a use-after-free vulnerability in the Linux kernel's SUNRPC client that occurs when cleaning up pipefs dentries. It allows attackers to potentially cause kernel crashes or execute arbitrary code with kernel privileges. Systems running affected Linux kernel versions with SUNRPC enabled are vulnerable.

💻 Affected Systems

Products:

Linux kernel

Versions: Specific affected versions not specified in CVE, but patches exist for multiple stable branches (see references).

Operating Systems: Linux distributions using vulnerable kernel versions

Default Config Vulnerable: ⚠️ Yes

Notes: Requires SUNRPC subsystem to be enabled and used. Common in NFS, CIFS, and other RPC-based services.

📦 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...

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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 privilege escalation to kernel-level code execution.

🟠

Likely Case

Kernel crash leading to denial of service, system instability, or memory corruption.

🟢

If Mitigated

Limited impact if SUNRPC is disabled or systems are not using RPC services.

🌐 Internet-Facing: MEDIUM - Requires RPC services to be exposed and accessible, which is common in network filesystem configurations.

🏢 Internal Only: MEDIUM - Internal RPC clients could trigger the vulnerability through normal operations.

🎯 Exploit Status

Public PoC: ✅ No

Weaponized: UNKNOWN

Unauthenticated Exploit: ✅ No

Complexity: HIGH - Requires specific timing conditions and RPC client operations.

Exploitation requires triggering the race condition during pipefs superblock reallocation.

🛠️ Fix & Mitigation

✅ Official Fix

Patch Version: Multiple stable kernel versions with fixes (see git references in CVE)

Vendor Advisory: https://git.kernel.org/stable/c/17866066b8ac1cc38fb449670bc15dc9fee4b40a

Restart Required: Yes

Instructions:

1. Identify current kernel version. 2. Apply appropriate kernel patch from git references. 3. Rebuild kernel if using custom build. 4. Reboot system to load patched kernel.

🔧 Temporary Workarounds

Disable SUNRPC

linux

Disable the SUNRPC subsystem if not required.

modprobe -r sunrpc
echo 'blacklist sunrpc' >> /etc/modprobe.d/blacklist.conf

Disable RPC-based services

linux

Disable NFS, CIFS, and other RPC-dependent services.

systemctl stop nfs-server
systemctl disable nfs-server

🧯 If You Can't Patch

Restrict RPC client usage to trusted applications only.
Implement strict network segmentation to limit RPC service exposure.

🔍 How to Verify

Check if Vulnerable:

Check kernel version and compare with patched versions in git references. Check if SUNRPC module is loaded: lsmod | grep sunrpc

Check Version:

uname -r

Verify Fix Applied:

Verify kernel version after update matches patched version. Check system logs for absence of KASAN reports related to dget_parent.

📡 Detection & Monitoring

Log Indicators:

KASAN reports of slab-use-after-free in dget_parent
Kernel panic messages
Workqueue errors in rpc_free_client_work

Network Indicators:

Unusual RPC traffic patterns
Multiple RPC connection failures

SIEM Query:

source="kernel" AND ("KASAN: slab-use-after-free" OR "dget_parent" OR "rpc_remove_pipedir")

📊 Metadata

CVE ID: CVE-2023-52803

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: May 21, 2024

Last Updated: September 23, 2025

🔗 References

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