CVE-2024-56626 – This CVE describes an out-of-bounds write vulne... (How to Fix)

Q: What is the severity of CVE-2024-56626?

CVE-2024-56626 has a CVSS score of 7.8 (HIGH). This CVE describes an out-of-bounds write vulnerability in the Linux kernel's ksmbd SMB server component. When 'vfs objects = streams_xattr' is configured in ksmbd.conf, a malicious client can send a negative offset value, allowing them to write data outside allocated buffer boundaries. This affects Linux systems running ksmbd with the vulnerable configuration.

📋 TL;DR

This CVE describes an out-of-bounds write vulnerability in the Linux kernel's ksmbd SMB server component. When 'vfs objects = streams_xattr' is configured in ksmbd.conf, a malicious client can send a negative offset value, allowing them to write data outside allocated buffer boundaries. This affects Linux systems running ksmbd with the vulnerable configuration.

💻 Affected Systems

Products:

Linux kernel with ksmbd module

Versions: Linux kernel versions with vulnerable ksmbd implementation before patches were applied

Operating Systems: Linux distributions using affected kernel versions

Default Config Vulnerable: ✅ No

Notes: Only vulnerable when 'vfs objects = streams_xattr' is explicitly set in ksmbd.conf configuration file.

📦 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

Full system compromise via kernel memory corruption leading to arbitrary code execution with kernel privileges, potentially resulting in complete system takeover.

🟠

Likely Case

Kernel panic or system crash causing denial of service, with potential for limited privilege escalation depending on exploit sophistication.

🟢

If Mitigated

No impact if streams_xattr is not enabled in ksmbd.conf configuration.

🌐 Internet-Facing: MEDIUM - Requires ksmbd service to be exposed and streams_xattr enabled, but SMB services are commonly internet-facing.

🏢 Internal Only: HIGH - Internal attackers with network access to ksmbd service could exploit this for privilege escalation or DoS.

🎯 Exploit Status

Public PoC: ✅ No

Weaponized: UNKNOWN

Unauthenticated Exploit: ✅ No

Complexity: MEDIUM

Requires client access to ksmbd service and specific configuration. Exploitation involves sending crafted negative offset values.

🛠️ Fix & Mitigation

✅ Official Fix

Patch Version: Patched in kernel commits: 164d3597d26d9acff5d5b8bc3208bdcca942dd6a, 1aea5c9470be2c7129704fb1b9562b1e3e0576f8, 313dab082289e460391c82d855430ec8a28ddf81, 8cd7490fc0f268883e86e840cda5311257af69ca, c5797f195c67132d061d29c57a7c6d30530686f0

Vendor Advisory: https://git.kernel.org/stable/c/164d3597d26d9acff5d5b8bc3208bdcca942dd6a

Restart Required: Yes

Instructions:

1. Update Linux kernel to version containing the fix. 2. Check with your distribution for security updates. 3. Reboot system to load new kernel.

🔧 Temporary Workarounds

Disable streams_xattr in ksmbd.conf

linux

Remove or comment out 'vfs objects = streams_xattr' line from ksmbd.conf configuration file

sed -i 's/vfs objects = streams_xattr/#vfs objects = streams_xattr/g' /etc/ksmbd/ksmbd.conf
systemctl restart ksmbd

Disable ksmbd service

linux

Stop and disable ksmbd service if not required

systemctl stop ksmbd
systemctl disable ksmbd

🧯 If You Can't Patch

Remove 'vfs objects = streams_xattr' from ksmbd.conf configuration
Restrict network access to ksmbd service using firewall rules

🔍 How to Verify

Check if Vulnerable:

Check if ksmbd is running and if /etc/ksmbd/ksmbd.conf contains 'vfs objects = streams_xattr' line

Check Version:

uname -r

Verify Fix Applied:

Verify kernel version includes the fix commits and check ksmbd.conf no longer has vulnerable configuration

📡 Detection & Monitoring

Log Indicators:

Kernel panic logs
ksmbd crash logs
Unexpected memory access errors in kernel logs

Network Indicators:

Unusual SMB traffic with negative offset values
Multiple connection attempts to ksmbd port

SIEM Query:

source="kernel" AND ("panic" OR "oops" OR "segfault") AND process="ksmbd"

📊 Metadata

CVE ID: CVE-2024-56626

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-787

Published: December 27, 2024

Last Updated: November 3, 2025

🔗 References

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🔗 Related Vulnerabilities

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