CVE-2023-52434 – This CVE-2023-52434 is an out-of-bounds read vu... (How to Fix)

Q: What is the severity of CVE-2023-52434?

CVE-2023-52434 has a CVSS score of 8.0 (HIGH). This CVE-2023-52434 is an out-of-bounds read vulnerability in the Linux kernel's SMB client implementation. It allows attackers to trigger kernel crashes (denial of service) or potentially leak kernel memory information when a malicious SMB server sends specially crafted create contexts. Any system using the affected Linux kernel with CIFS/SMB client functionality is vulnerable.

📋 TL;DR

This CVE-2023-52434 is an out-of-bounds read vulnerability in the Linux kernel's SMB client implementation. It allows attackers to trigger kernel crashes (denial of service) or potentially leak kernel memory information when a malicious SMB server sends specially crafted create contexts. Any system using the affected Linux kernel with CIFS/SMB client functionality is vulnerable.

💻 Affected Systems

Products:

Linux kernel

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

Operating Systems: Linux distributions using vulnerable kernel versions

Default Config Vulnerable: ⚠️ Yes

Notes: Only affects systems with CIFS/SMB client functionality enabled (common in most distributions). The vulnerability is triggered when mounting SMB shares.

📦 What is this software?

Debian Linux by Debian

View all CVEs affecting Debian Linux →

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 →

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 and denial of service, with potential for kernel memory information disclosure that could aid further exploitation.

🟠

Likely Case

System crash/panic when connecting to malicious SMB servers, causing denial of service and potential data loss from unsaved work.

🟢

If Mitigated

No impact if patched kernel is used or if SMB client functionality is disabled.

🌐 Internet-Facing: MEDIUM - Requires connecting to malicious SMB servers, which could be internet-facing shares or compromised servers.

🏢 Internal Only: MEDIUM - Internal malicious servers or compromised internal SMB servers could trigger the vulnerability.

🎯 Exploit Status

Public PoC: ✅ No

Weaponized: UNKNOWN

Unauthenticated Exploit: ✅ No

Complexity: MEDIUM

Exploitation requires control of an SMB server that the victim connects to. No authentication bypass is involved - the victim must mount/access the malicious share.

🛠️ Fix & Mitigation

✅ Official Fix

Patch Version: Kernel versions containing commits: 13fb0fc4917621f3dfa285a27eaf7151d770b5e5, 17a0f64cc02d4972e21c733d9f21d1c512963afa, 1ae3c59355dc9882e09c020afe8bd895ad0f29, 6726429c18c62dbf5e96ebbd522f262e016553fb, 890bc4fac3c0973a49cac35f634579bebba7fe48

Vendor Advisory: https://git.kernel.org/stable/c/13fb0fc4917621f3dfa285a27eaf7151d770b5e5

Restart Required: Yes

Instructions:

1. Update Linux kernel to patched version from your distribution's repositories. 2. Reboot system to load new kernel. 3. Verify kernel version after reboot.

🔧 Temporary Workarounds

Disable CIFS/SMB client module

linux

Prevent loading of the vulnerable kernel module

echo "install cifs /bin/false" >> /etc/modprobe.d/disable-cifs.conf
rmmod cifs 2>/dev/null || true

Restrict SMB mount access

linux

Limit which users can mount SMB shares

chmod 750 /sbin/mount.cifs
chown root:wheel /sbin/mount.cifs

🧯 If You Can't Patch

Implement network segmentation to restrict access to trusted SMB servers only
Monitor for unexpected system crashes or kernel panics related to SMB operations

🔍 How to Verify

Check if Vulnerable:

Check kernel version and compare with distribution's security advisories. Vulnerable if using unpatched kernel with CIFS support.

Check Version:

uname -r

Verify Fix Applied:

Check kernel version matches patched version from distribution. Test SMB mount functionality works normally.

📡 Detection & Monitoring

Log Indicators:

Kernel panic/Oops messages mentioning smb2_parse_contexts
System crashes during SMB mount operations
dmesg entries showing page faults in CIFS module

Network Indicators:

Unexpected connections to non-standard SMB servers
SMB traffic to unknown/untrusted IP addresses

SIEM Query:

source="kernel" AND ("smb2_parse_contexts" OR "CIFS" AND "page fault" OR "Oops")

📊 Metadata

CVE ID: CVE-2023-52434

CVSS v3 Score: 8.0 (HIGH)

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

CWE: CWE-119

Published: February 20, 2024

Last Updated: January 17, 2025

🔗 References

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🔗 Related Vulnerabilities

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