CVE-2024-35868 – This CVE describes a use-after-free vulnerabili... (How to Fix)

Q: What is the severity of CVE-2024-35868?

CVE-2024-35868 has a CVSS score of 7.8 (HIGH). This CVE describes a use-after-free vulnerability in the Linux kernel's SMB client implementation. An attacker could potentially exploit this to crash the kernel or execute arbitrary code. Systems running vulnerable Linux kernel versions with SMB client functionality are affected.

📋 TL;DR

This CVE describes a use-after-free vulnerability in the Linux kernel's SMB client implementation. An attacker could potentially exploit this to crash the kernel or execute arbitrary code. Systems running vulnerable Linux kernel versions with SMB client functionality are affected.

💻 Affected Systems

Products:

Linux kernel

Versions: Specific affected versions not explicitly stated in CVE description; check kernel commit history for exact ranges.

Operating Systems: Linux distributions using vulnerable kernel versions

Default Config Vulnerable: ⚠️ Yes

Notes: Requires SMB client functionality and access to write to /proc/fs/cifs/Stats.

📦 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 →

⚠️ Risk & Real-World Impact

🔴

Worst Case

Kernel panic leading to system crash or potential arbitrary code execution with kernel privileges, resulting in complete system compromise.

🟠

Likely Case

Kernel crash leading to denial of service and system instability.

🟢

If Mitigated

Limited impact if proper access controls prevent unauthorized users from writing to /proc/fs/cifs/Stats.

🌐 Internet-Facing: LOW - Requires local access to the system to write to procfs.

🏢 Internal Only: MEDIUM - Local users or processes could potentially exploit this vulnerability.

🎯 Exploit Status

Public PoC: ✅ No

Weaponized: UNKNOWN

Unauthenticated Exploit: ✅ No

Complexity: MEDIUM

Exploitation requires local access and ability to write to specific procfs entry during session teardown.

🛠️ Fix & Mitigation

✅ Official Fix

Patch Version: Kernel versions containing commits: 5b5475ce69f02ecc1b13ea23106e5b89c690429b, 8fefd166fcb368c5fcf48238e3f7c8af829e0a72, cf03020c56d3ed28c4942280957a007b5e9544f7, d3da25c5ac84430f89875ca7485a3828150a7e0a

Vendor Advisory: https://git.kernel.org/stable/c/5b5475ce69f02ecc1b13ea23106e5b89c690429b

Restart Required: Yes

Instructions:

1. Update Linux kernel to patched version. 2. Check distribution-specific security advisories. 3. Reboot system after kernel update.

🔧 Temporary Workarounds

Restrict procfs access

linux

Limit access to /proc/fs/cifs/Stats to prevent unauthorized writes

chmod 600 /proc/fs/cifs/Stats
chown root:root /proc/fs/cifs/Stats

Disable SMB client if not needed

linux

Remove or disable SMB client functionality

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

🧯 If You Can't Patch

Implement strict access controls to limit who can write to /proc/fs/cifs/Stats
Monitor system logs for kernel crashes or suspicious activity related to SMB sessions

🔍 How to Verify

Check if Vulnerable:

Check kernel version and verify if it contains the vulnerable code by examining kernel source or distribution security advisories.

Check Version:

uname -r

Verify Fix Applied:

Verify kernel version includes the fix commits or check with 'uname -r' and compare against patched versions from your distribution.

📡 Detection & Monitoring

Log Indicators:

Kernel panic messages
Oops messages in dmesg
Unexpected system crashes

Network Indicators:

Unusual SMB client activity patterns

SIEM Query:

source="kernel" AND ("Oops" OR "panic" OR "BUG") AND "cifs"

📊 Metadata

CVE ID: CVE-2024-35868

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 19, 2024

Last Updated: December 30, 2024

🔗 References

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🔗 Related Vulnerabilities

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