CVE-2021-27219 – CVE-2021-27219 is an integer overflow vulnerabi... (How to Fix)

Q: What is the severity of CVE-2021-27219?

CVE-2021-27219 has a CVSS score of 7.5 (HIGH). CVE-2021-27219 is an integer overflow vulnerability in GNOME GLib's g_bytes_new function on 64-bit platforms, caused by an implicit cast from 64-bit to 32-bit values. This can lead to memory corruption, potentially allowing attackers to execute arbitrary code or cause denial of service. Systems using vulnerable versions of GLib (especially on 64-bit Linux distributions) are affected.

📋 TL;DR

CVE-2021-27219 is an integer overflow vulnerability in GNOME GLib's g_bytes_new function on 64-bit platforms, caused by an implicit cast from 64-bit to 32-bit values. This can lead to memory corruption, potentially allowing attackers to execute arbitrary code or cause denial of service. Systems using vulnerable versions of GLib (especially on 64-bit Linux distributions) are affected.

💻 Affected Systems

Products:

GNOME GLib
Applications using GLib library

Versions: GLib versions before 2.66.6 and 2.67.x before 2.67.3

Operating Systems: Linux distributions (Debian, Fedora, Ubuntu, etc.), Other Unix-like systems

Default Config Vulnerable: ⚠️ Yes

Notes: Only affects 64-bit platforms. Many Linux applications and desktop environments depend on GLib.

📦 What is this software?

⚠️ Risk & Real-World Impact

🔴

Worst Case

Remote code execution leading to complete system compromise if exploited in network-facing services using GLib.

🟠

Likely Case

Application crash or denial of service due to memory corruption, with potential for limited code execution in specific contexts.

🟢

If Mitigated

Minimal impact if applications have proper memory protections (ASLR, DEP) and input validation.

🌐 Internet-Facing: MEDIUM - Exploitation requires specific conditions but could affect network services using GLib.

🏢 Internal Only: LOW - Requires local access or exploitation through other compromised applications.

🎯 Exploit Status

Public PoC: ✅ No

Weaponized: UNKNOWN

Unauthenticated Exploit: ✅ No

Complexity: HIGH - Requires specific conditions and memory manipulation expertise.

No publicly available exploit code. Exploitation requires triggering the integer overflow with specific input sizes.

🛠️ Fix & Mitigation

✅ Official Fix

Patch Version: GLib 2.66.6 or 2.67.3 and later

Vendor Advisory: https://gitlab.gnome.org/GNOME/glib/-/issues/2319

Restart Required: Yes

Instructions:

1. Update GLib package using system package manager. 2. For Debian/Ubuntu: sudo apt update && sudo apt upgrade libglib2.0-0. 3. For Fedora/RHEL: sudo dnf update glib2. 4. Restart affected services or reboot system.

🔧 Temporary Workarounds

Input validation in applications

all

Implement strict input size validation in applications using g_bytes_new to prevent triggering the overflow.

🧯 If You Can't Patch

Restrict network access to services using vulnerable GLib versions
Implement application sandboxing or containerization to limit potential damage

🔍 How to Verify

Check if Vulnerable:

Check GLib version: dpkg -l libglib2.0-0 | grep ^ii on Debian/Ubuntu, or rpm -q glib2 on RHEL/Fedora.

Check Version:

pkg-config --modversion glib-2.0

Verify Fix Applied:

Verify version is 2.66.6 or higher (stable) or 2.67.3+ (development).

📡 Detection & Monitoring

Log Indicators:

Application crashes with segmentation faults
Memory corruption errors in system logs

Network Indicators:

Unusual network traffic to services using GLib

SIEM Query:

source="application_logs" AND ("segmentation fault" OR "memory corruption") AND process="*glib*"

📊 Metadata

CVE ID: CVE-2021-27219

CVSS v3 Score: 7.5 (HIGH)

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

CWE: CWE-681

Published: February 15, 2021

Last Updated: November 21, 2024

🔗 References

https://gitlab.gnome.org/GNOME/glib/-/issues/2319 Exploit,Issue Tracking,Third Party Advisory
https://lists.apache.org/thread.html/rf9fa47ab66495c78bb4120b0754dd9531ca2ff0430f6685ac9b07772%40%3Cdev.mina.apache.org%3E
https://lists.debian.org/debian-lts-announce/2022/06/msg00006.html Mailing List,Third Party Advisory
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/2REA7RVKN7ZHRLJOEGBRQKJIPZQPAELZ/
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/JJMPNDO4GDVURYQFYKFOWY5HAF4FTEPN/
https://security.gentoo.org/glsa/202107-13 Third Party Advisory
https://security.netapp.com/advisory/ntap-20210319-0004/ Third Party Advisory
https://gitlab.gnome.org/GNOME/glib/-/issues/2319 Exploit,Issue Tracking,Third Party Advisory
https://lists.apache.org/thread.html/rf9fa47ab66495c78bb4120b0754dd9531ca2ff0430f6685ac9b07772%40%3Cdev.mina.apache.org%3E
https://lists.debian.org/debian-lts-announce/2022/06/msg00006.html Mailing List,Third Party Advisory
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/2REA7RVKN7ZHRLJOEGBRQKJIPZQPAELZ/
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/JJMPNDO4GDVURYQFYKFOWY5HAF4FTEPN/
https://security.gentoo.org/glsa/202107-13 Third Party Advisory
https://security.netapp.com/advisory/ntap-20210319-0004/ Third Party Advisory

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