CVE-2024-27036 – A writeback data corruption vulnerability in th... (How to Fix)

Q: What is the severity of CVE-2024-27036?

CVE-2024-27036 has a CVSS score of 7.8 (HIGH). A writeback data corruption vulnerability in the Linux kernel's CIFS filesystem implementation allows attackers to corrupt files written to CIFS shares. This affects systems using CIFS/SMB mounts with specific wsize configurations. The corruption occurs when writing files larger than the configured wsize, potentially leading to data integrity issues.

📋 TL;DR

A writeback data corruption vulnerability in the Linux kernel's CIFS filesystem implementation allows attackers to corrupt files written to CIFS shares. This affects systems using CIFS/SMB mounts with specific wsize configurations. The corruption occurs when writing files larger than the configured wsize, potentially leading to data integrity issues.

💻 Affected Systems

Products:

Linux kernel

Versions: Specific affected kernel versions not specified in CVE, but fix commits indicate vulnerability existed before patches were applied. Check kernel versions containing the fix commits.

Operating Systems: Linux distributions using vulnerable kernel versions

Default Config Vulnerable: ⚠️ Yes

Notes: Only affects systems with CIFS mounts configured with wsize smaller than files being written. The vulnerability manifests during write operations to CIFS shares.

📦 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

Critical data corruption in files written to CIFS shares, potentially affecting system stability, application functionality, or causing data loss.

🟠

Likely Case

File corruption when writing files larger than the configured wsize to CIFS mounts, leading to data integrity issues and potential application failures.

🟢

If Mitigated

Minimal impact if systems are patched or use workarounds like adjusting wsize or avoiding vulnerable configurations.

🌐 Internet-Facing: MEDIUM - Requires CIFS mounts to internet-facing shares, which is less common than internal file sharing.

🏢 Internal Only: HIGH - Internal CIFS/SMB file sharing is common in enterprise environments, making many internal systems vulnerable.

🎯 Exploit Status

Public PoC: ⚠️ Yes

Weaponized: LIKELY

Unauthenticated Exploit: ✅ No

Complexity: LOW

The CVE includes a test case demonstrating the vulnerability. Exploitation requires write access to CIFS mounts and specific file operations.

🛠️ Fix & Mitigation

✅ Official Fix

Patch Version: Kernel versions containing commits: 65f2ced695982ccd516196d0a9447d85dbe2eed5, 844b4e132f57f1333dc79feaa035075a096762e4, e45deec35bf7f1f4f992a707b2d04a8c162f2240, f3dc1bdb6b0b0693562c7c54a6c28bafa608ba3c

Vendor Advisory: https://git.kernel.org/stable/c/65f2ced695982ccd516196d0a9447d85dbe2eed5

Restart Required: Yes

Instructions:

1. Update Linux kernel to version containing the fix commits. 2. Reboot system to load new kernel. 3. Verify kernel version after reboot.

🔧 Temporary Workarounds

Adjust CIFS wsize parameter

linux

Increase wsize to be larger than typical file writes to avoid the corruption condition

mount -o wsize=65536 //server/share /mnt

Avoid CIFS for large file transfers

all

Use alternative protocols (NFS, SFTP) for files larger than wsize

🧯 If You Can't Patch

Disable CIFS mounts or use alternative file sharing protocols
Implement file integrity monitoring on CIFS shares to detect corruption

🔍 How to Verify

Check if Vulnerable:

Test with provided dd/cp/cmp commands using wsize=64000 as described in CVE

Check Version:

uname -r

Verify Fix Applied:

Run the same test after patching - cmp should succeed without corruption

📡 Detection & Monitoring

Log Indicators:

File corruption errors in application logs
CIFS write errors in kernel logs

Network Indicators:

Unusual SMB write patterns or retransmissions

SIEM Query:

source="kernel" AND "CIFS" AND ("write" OR "corrupt")

📊 Metadata

CVE ID: CVE-2024-27036

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: May 1, 2024

Last Updated: September 18, 2025

🔗 References

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🔗 Related Vulnerabilities

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