CVE-2024-49996 – This CVE describes a buffer overflow vulnerabil... (How to Fix)

Q: What is the severity of CVE-2024-49996?

CVE-2024-49996 has a CVSS score of 7.8 (HIGH). This CVE describes a buffer overflow vulnerability in the Linux kernel's CIFS filesystem driver when parsing NFS reparse points. An attacker could exploit this to cause a kernel crash (denial of service) or potentially execute arbitrary code. Systems using CIFS mounts with NFS reparse point support are affected.

📋 TL;DR

This CVE describes a buffer overflow vulnerability in the Linux kernel's CIFS filesystem driver when parsing NFS reparse points. An attacker could exploit this to cause a kernel crash (denial of service) or potentially execute arbitrary code. Systems using CIFS mounts with NFS reparse point support are affected.

💻 Affected Systems

Products:

Linux kernel

Versions: Specific affected versions not specified in CVE, but patches exist in stable kernel trees.

Operating Systems: Linux distributions using vulnerable kernel versions

Default Config Vulnerable: ⚠️ Yes

Notes: Requires CIFS filesystem mounting with NFS reparse point support enabled.

📦 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

Kernel memory corruption leading to arbitrary code execution with kernel privileges, resulting in complete system compromise.

🟠

Likely Case

Kernel panic or system crash causing denial of service, requiring system reboot.

🟢

If Mitigated

Limited impact if CIFS mounts are restricted or NFS reparse point support is disabled.

🌐 Internet-Facing: MEDIUM - Requires CIFS mount access, which may be exposed in some configurations.

🏢 Internal Only: MEDIUM - Internal attackers with CIFS mount access could exploit this vulnerability.

🎯 Exploit Status

Public PoC: ✅ No

Weaponized: UNKNOWN

Unauthenticated Exploit: ✅ No

Complexity: MEDIUM

Exploitation requires access to create or modify NFS reparse points on a CIFS mount.

🛠️ Fix & Mitigation

✅ Official Fix

Patch Version: Patches available in stable kernel trees (commits: 01cdddde39b065074fd48f07027757783cbf5b7d, 73b078e3314d4854fd8286f3ba65c860ddd3a3dd, 7b222d6cb87077faf56a687a72af1951cf78c8a9, 803b3a39cb096d8718c0aebc03fd19f11c7dc919, c173d47b69f07cd7ca08efb4e458adbd4725d8e9)

Vendor Advisory: https://git.kernel.org/stable/c/01cdddde39b065074fd48f07027757783cbf5b7d

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 mounts

linux

Remove or unmount CIFS filesystems to eliminate attack surface.

umount /path/to/cifs/mount
Remove CIFS entries from /etc/fstab

Restrict CIFS mount access

linux

Limit access to CIFS mounts to trusted users only.

chmod 700 /path/to/cifs/mount
Set appropriate mount options in /etc/fstab

🧯 If You Can't Patch

Implement strict access controls on CIFS mounts
Monitor for unusual activity on CIFS mounts and kernel crash logs

🔍 How to Verify

Check if Vulnerable:

Check if CIFS mounts are in use and kernel version is unpatched: 'mount | grep cifs' and 'uname -r'

Check Version:

uname -r

Verify Fix Applied:

Verify kernel version after update matches patched version and test CIFS mount functionality.

📡 Detection & Monitoring

Log Indicators:

Kernel panic messages
CIFS-related errors in dmesg
System crash/reboot events

Network Indicators:

Unusual CIFS traffic patterns
Multiple connection attempts to CIFS shares

SIEM Query:

source="kernel" AND ("panic" OR "oops") AND ("cifs" OR "buffer overflow")

📊 Metadata

CVE ID: CVE-2024-49996

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-120

Published: October 21, 2024

Last Updated: November 3, 2025

🔗 References

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