CVE-2022-50511

5.5 MEDIUM
Denial of Service

📋 TL;DR

This CVE-2022-50511 is a Linux kernel vulnerability in the font handling subsystem where a signed integer shift operation causes undefined behavior, potentially leading to kernel instability or crashes. It affects Linux systems with framebuffer console support enabled. The vulnerability is triggered during console initialization when specific font configurations are loaded.

💻 Affected Systems

Products:
  • Linux kernel
Versions: Linux kernel versions before the fix commits (specific versions vary by distribution)
Operating Systems: Linux distributions using affected kernel versions
Default Config Vulnerable: ⚠️ Yes
Notes: Requires framebuffer console support (CONFIG_FRAMEBUFFER_CONSOLE) and font subsystem usage. Most desktop/server Linux installations are potentially affected.

⚠️ Risk & Real-World Impact

🔴

Worst Case

Kernel panic or system crash due to undefined behavior in kernel space, potentially causing denial of service and system instability.

🟠

Likely Case

System instability or kernel warnings (UBSAN) during console/framebuffer initialization, possibly preventing proper display console setup.

🟢

If Mitigated

Minor performance impact or warning messages during boot if UBSAN is enabled, but system remains functional.

🌐 Internet-Facing: LOW - This vulnerability requires local access or specific kernel module loading to trigger, not directly exploitable over network.
🏢 Internal Only: MEDIUM - Local users or processes triggering framebuffer console initialization could cause system instability or crashes.

🎯 Exploit Status

Public PoC: ✅ No
Weaponized: NO
Unauthenticated Exploit: ✅ No
Complexity: MEDIUM

Exploitation requires triggering the vulnerable code path through console/framebuffer initialization, typically requiring local access or specific kernel module loading.

🛠️ Fix & Mitigation

✅ Official Fix

Patch Version: Fixed in kernel commits: 6fe888c4d2fb174408e4540bb2d5602b9f507f90, 890d91b31f4874361e0df047f57d268a7021cb12, 9c14a85e18a58c102ec223144b7edb5b345c1bea, c9a9aa02f0fa3318e0ae5774f404419a1b4759ca, e039929e36818507e90901edae87f6fa8bc81093

Vendor Advisory: https://git.kernel.org/stable/c/6fe888c4d2fb174408e4540bb2d5602b9f507f90

Restart Required: Yes

Instructions:

1. Update Linux kernel to version containing the fix commits. 2. For distributions: Use package manager (apt/yum/dnf) to update kernel package. 3. Reboot system to load new kernel.

🔧 Temporary Workarounds

Disable framebuffer console

linux

Remove framebuffer console support to avoid triggering vulnerable code path

Remove 'CONFIG_FRAMEBUFFER_CONSOLE' from kernel configuration and rebuild kernel

Disable UBSAN warnings

linux

Turn off undefined behavior sanitizer to prevent warnings but doesn't fix vulnerability

Add 'ubsan=0' to kernel boot parameters in GRUB configuration

🧯 If You Can't Patch

  • Restrict local user access to systems with vulnerable kernels
  • Monitor system logs for UBSAN warnings related to font subsystem

🔍 How to Verify

Check if Vulnerable:

Check kernel version and compare with distribution's patched versions. Look for UBSAN warnings in dmesg during boot.

Check Version:

uname -r

Verify Fix Applied:

Verify kernel version includes fix commits. Check that 'CONFIG_FRAMEBUFFER_CONSOLE' is properly configured if needed.

📡 Detection & Monitoring

Log Indicators:

  • UBSAN warnings in kernel logs (dmesg) about shift-out-of-bounds in lib/fonts/fonts.c
  • Kernel panic messages during console initialization

Network Indicators:

  • None - local vulnerability only

SIEM Query:

source="kernel" AND ("UBSAN: shift-out-of-bounds" OR "lib/fonts/fonts.c" OR "get_default_font")

📊 Metadata

CVE ID: CVE-2022-50511
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
Published: October 7, 2025
Last Updated: February 5, 2026

🤖 AI-assisted analysis, reviewed for accuracy

🔗 References

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