CVE-2022-49586 – This CVE describes a race condition vulnerabili... (How to Fix)

Q: What is the severity of CVE-2022-49586?

CVE-2022-49586 has a CVSS score of 4.7 (MEDIUM). This CVE describes a race condition vulnerability in the Linux kernel's TCP Fast Open implementation. When multiple threads read the sysctl_tcp_fastopen configuration variable simultaneously while it's being modified, they may read inconsistent values, potentially leading to unexpected network behavior. This affects all Linux systems using TCP Fast Open functionality.

📋 TL;DR

This CVE describes a race condition vulnerability in the Linux kernel's TCP Fast Open implementation. When multiple threads read the sysctl_tcp_fastopen configuration variable simultaneously while it's being modified, they may read inconsistent values, potentially leading to unexpected network behavior. This affects all Linux systems using TCP Fast Open functionality.

💻 Affected Systems

Products:

Linux Kernel

Versions: Specific affected versions not specified in CVE; likely multiple stable kernel versions before fixes were applied

Operating Systems: Linux distributions using vulnerable kernel versions

Default Config Vulnerable: ⚠️ Yes

Notes: Only affects systems with TCP Fast Open enabled and where sysctl_tcp_fastopen is being modified while read by multiple threads.

📦 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...

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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 →

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 →

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

Inconsistent TCP Fast Open behavior could cause connection failures, performance degradation, or potential denial of service for network services relying on TCP connections.

🟠

Likely Case

Minor network instability or connection issues in high-concurrency environments where sysctl_tcp_fastopen is frequently modified while being read.

🟢

If Mitigated

No impact if proper synchronization is implemented or if TCP Fast Open is disabled.

🌐 Internet-Facing: LOW - Requires local access to modify sysctl parameters and specific timing conditions to trigger race condition.

🏢 Internal Only: LOW - Same constraints apply; requires privileged access and specific timing conditions.

🎯 Exploit Status

Public PoC: ✅ No

Weaponized: NO

Unauthenticated Exploit: ✅ No

Complexity: HIGH - Requires race condition timing and privileged access to modify sysctl parameters

This is a data race vulnerability that requires specific timing conditions and privileged access to trigger.

🛠️ Fix & Mitigation

✅ Official Fix

Patch Version: Multiple stable kernel commits listed in references

Vendor Advisory: https://git.kernel.org/stable/c/03da610696a32578fc4f986479341ce9d430df08

Restart Required: Yes

Instructions:

1. Update Linux kernel to version containing fixes 2. Reboot system 3. Verify kernel version after reboot

🔧 Temporary Workarounds

Disable TCP Fast Open

linux

Disables the vulnerable functionality entirely

echo 0 > /proc/sys/net/ipv4/tcp_fastopen

🧯 If You Can't Patch

Avoid modifying sysctl_tcp_fastopen parameter while system is under high load
Implement application-level connection retry logic to handle potential TCP connection issues

🔍 How to Verify

Check if Vulnerable:

Check kernel version against known vulnerable versions and verify if TCP Fast Open is enabled: cat /proc/sys/net/ipv4/tcp_fastopen

Check Version:

uname -r

Verify Fix Applied:

Verify kernel version is updated to include the fix commits and test TCP Fast Open functionality

📡 Detection & Monitoring

Log Indicators:

Kernel logs showing TCP connection failures or unexpected network behavior

Network Indicators:

TCP connection timeouts or failures when Fast Open is expected to work

SIEM Query:

Search for kernel logs containing 'TCP' and 'FastOpen' errors or connection failures

📊 Metadata

CVE ID: CVE-2022-49586

CVSS v3 Score: 4.7 (MEDIUM)

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

CWE: CWE-362

EPSS Score: 0.03% exploit probability (7.2th percentile)

Published: February 26, 2025

Last Updated: October 1, 2025

🔗 References

📤 Share & Export

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🔗 Related Vulnerabilities

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