CVE-2022-49821 – This CVE describes a memory leak vulnerability ... (How to Fix)

Q: What is the severity of CVE-2022-49821?

CVE-2022-49821 has a CVSS score of 5.5 (MEDIUM). This CVE describes a memory leak vulnerability in the Linux kernel's mISDN driver. When the mISDN_dsp_element_register() function fails to properly release device references, it can cause kernel memory exhaustion over time. Systems using the mISDN subsystem for ISDN telephony services are affected.

📋 TL;DR

This CVE describes a memory leak vulnerability in the Linux kernel's mISDN driver. When the mISDN_dsp_element_register() function fails to properly release device references, it can cause kernel memory exhaustion over time. Systems using the mISDN subsystem for ISDN telephony services are affected.

💻 Affected Systems

Products:

Linux kernel

Versions: Kernel versions before the fix commits (specific versions vary by distribution)

Operating Systems: Linux distributions with mISDN support enabled

Default Config Vulnerable: ✅ No

Notes: Only vulnerable if mISDN subsystem is compiled into the kernel or loaded as a module. Most standard distributions don't enable mISDN 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...

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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

Sustained exploitation could lead to kernel memory exhaustion, causing system instability, denial of service, or potential kernel crashes.

🟠

Likely Case

Gradual memory consumption leading to performance degradation and eventual system instability requiring reboot.

🟢

If Mitigated

Minimal impact with proper monitoring and memory limits in place.

🌐 Internet-Facing: LOW - mISDN is typically used for internal telephony infrastructure, not directly internet-exposed.

🏢 Internal Only: MEDIUM - Affects systems using mISDN for telephony services, which could impact internal communications.

🎯 Exploit Status

Public PoC: ✅ No

Weaponized: NO

Unauthenticated Exploit: ✅ No

Complexity: MEDIUM

Exploitation requires local access or ability to trigger mISDN operations. Memory leak requires repeated triggering to cause significant impact.

🛠️ Fix & Mitigation

✅ Official Fix

Patch Version: Fixed in kernel commits: 083a2c9ef82e184bdf0b9f9a1e5fc38d32afbb47, 0f2c681900a01e3f23789bca26d88268c3d5b51d, 727ed7d28348c026c7ef4d852f3d0e5054d376e8, 7a05e3929668c8cfef495c69752a9e91fac4878f, 98a2ac1ca8fd6eca6867726fe238d06e75eb1acd

Vendor Advisory: https://git.kernel.org/stable/c/083a2c9ef82e184bdf0b9f9a1e5fc38d32afbb47

Restart Required: Yes

Instructions:

1. Update Linux kernel to version containing the fix commits. 2. Check distribution-specific security advisories. 3. Reboot system after kernel update.

🔧 Temporary Workarounds

Disable mISDN module

linux

Unload mISDN kernel module if not required

sudo rmmod mISDN_core
sudo rmmod mISDN_dsp
echo 'blacklist mISDN_core' | sudo tee /etc/modprobe.d/blacklist-misdn.conf
echo 'blacklist mISDN_dsp' | sudo tee -a /etc/modprobe.d/blacklist-misdn.conf

🧯 If You Can't Patch

Monitor kernel memory usage for abnormal increases
Implement system monitoring to detect memory exhaustion events

🔍 How to Verify

Check if Vulnerable:

Check if mISDN modules are loaded: lsmod | grep -i misdn

Check Version:

uname -r

Verify Fix Applied:

Check kernel version contains fix commits: uname -r and verify with distribution security advisories

📡 Detection & Monitoring

Log Indicators:

Kernel oom-killer messages
System memory exhaustion warnings
mISDN module loading/unloading events

Network Indicators:

Unusual mISDN telephony traffic patterns

SIEM Query:

source="kernel" AND ("out of memory" OR "oom-killer" OR "mISDN")

📊 Metadata

CVE ID: CVE-2022-49821

CVSS v3 Score: 5.5 (MEDIUM)

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

CWE: CWE-401

EPSS Score: 0.02% exploit probability (5.7th percentile)

Published: May 1, 2025

Last Updated: November 10, 2025

🔗 References

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