CVE-2025-21718 – This CVE-2025-21718 is a race condition vulnera... (How to Fix)

Q: What is the severity of CVE-2025-21718?

CVE-2025-21718 has a CVSS score of 7.0 (HIGH). This CVE-2025-21718 is a race condition vulnerability in the Linux kernel's ROSE protocol implementation where timers can access freed socket memory. It allows potential use-after-free conditions that could lead to kernel crashes or privilege escalation. Systems running vulnerable Linux kernel versions with ROSE protocol enabled are affected.

📋 TL;DR

This CVE-2025-21718 is a race condition vulnerability in the Linux kernel's ROSE protocol implementation where timers can access freed socket memory. It allows potential use-after-free conditions that could lead to kernel crashes or privilege escalation. Systems running vulnerable Linux kernel versions with ROSE protocol enabled are affected.

💻 Affected Systems

Products:

Linux kernel

Versions: Versions before the fix commits (specific versions depend on distribution backports)

Operating Systems: Linux distributions with vulnerable kernel versions

Default Config Vulnerable: ✅ No

Notes: Only vulnerable if ROSE (X.25 PLP) protocol is enabled and in use. Most modern systems don't use ROSE by default.

📦 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 →

⚠️ Risk & Real-World Impact

🔴

Worst Case

Kernel panic leading to system crash, or potential privilege escalation to root if an attacker can manipulate the freed memory region.

🟠

Likely Case

System instability, kernel crashes, or denial of service affecting network connectivity.

🟢

If Mitigated

Minimal impact if ROSE protocol is disabled or systems are isolated from untrusted users.

🌐 Internet-Facing: LOW (ROSE protocol is rarely used on internet-facing systems)

🏢 Internal Only: MEDIUM (requires local access or network access to ROSE services)

🎯 Exploit Status

Public PoC: ✅ No

Weaponized: UNKNOWN

Unauthenticated Exploit: ✅ No

Complexity: MEDIUM

Requires race condition timing and ROSE protocol access. Likely requires local access or network access to ROSE services.

🛠️ Fix & Mitigation

✅ Official Fix

Patch Version: Kernel versions containing commits 0d5bca3be27bfcf8f980f2fed49b6cbb7dafe4a1 or later

Vendor Advisory: https://git.kernel.org/stable/c/0d5bca3be27bfcf8f980f2fed49b6cbb7dafe4a1

Restart Required: Yes

Instructions:

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

🔧 Temporary Workarounds

Disable ROSE protocol

Linux

Disable the ROSE (X.25 PLP) protocol module if not needed

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

🧯 If You Can't Patch

Disable ROSE protocol module entirely if not required
Restrict access to systems using ROSE protocol to trusted users only

🔍 How to Verify

Check if Vulnerable:

Check if ROSE module is loaded: lsmod | grep rose. If loaded and kernel version is vulnerable, system is at risk.

Check Version:

uname -r

Verify Fix Applied:

Check kernel version is patched and ROSE module can be safely loaded if needed.

📡 Detection & Monitoring

Log Indicators:

Kernel panic messages
KASAN use-after-free reports in dmesg
System crashes related to rose_timer

Network Indicators:

Unusual ROSE protocol traffic from untrusted sources

SIEM Query:

kernel: *rose_timer* OR *KASAN: *use-after-free* OR *BUG: *slab-use-after-free*

📊 Metadata

CVE ID: CVE-2025-21718

CVSS v3 Score: 7.0 (HIGH)

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

CWE: CWE-362

EPSS Score: 0.02% exploit probability (5.6th percentile)

Published: February 27, 2025

Last Updated: November 3, 2025

🔗 References

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🔗 Related Vulnerabilities

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