CVE-2021-23169 – CVE-2021-23169 is a heap-buffer overflow vulner... (How to Fix)

Q: What is the severity of CVE-2021-23169?

CVE-2021-23169 has a CVSS score of 8.8 (HIGH). CVE-2021-23169 is a heap-buffer overflow vulnerability in OpenEXR's copyIntoFrameBuffer function that allows attackers to execute arbitrary code with the permissions of the user running the vulnerable application. This affects any application compiled against OpenEXR versions before 3.0.1 that processes malicious image files.

📋 TL;DR

CVE-2021-23169 is a heap-buffer overflow vulnerability in OpenEXR's copyIntoFrameBuffer function that allows attackers to execute arbitrary code with the permissions of the user running the vulnerable application. This affects any application compiled against OpenEXR versions before 3.0.1 that processes malicious image files.

💻 Affected Systems

Products:

OpenEXR
Applications compiled against OpenEXR library

Versions: All versions before 3.0.1

Operating Systems: Linux, Windows, macOS, Unix-like systems

Default Config Vulnerable: ⚠️ Yes

Notes: Any application using OpenEXR to process EXR image files is vulnerable. Common in media, VFX, and graphics applications.

📦 What is this software?

⚠️ Risk & Real-World Impact

🔴

Worst Case

Full remote code execution leading to complete system compromise, data theft, or ransomware deployment.

🟠

Likely Case

Application crash (denial of service) or limited code execution depending on exploit sophistication.

🟢

If Mitigated

No impact if patched or if application runs with minimal privileges and input validation.

🌐 Internet-Facing: MEDIUM - Requires processing malicious image files, which could be uploaded via web interfaces or email attachments.

🏢 Internal Only: LOW - Typically requires user interaction to open malicious files, though automated processing systems could be at risk.

🎯 Exploit Status

Public PoC: ⚠️ Yes

Weaponized: LIKELY

Unauthenticated Exploit: ✅ No

Complexity: MEDIUM

Exploitation requires the victim to process a specially crafted EXR image file. No authentication bypass needed beyond file access.

🛠️ Fix & Mitigation

✅ Official Fix

Patch Version: 3.0.1 and later

Vendor Advisory: https://github.com/AcademySoftwareFoundation/openexr/releases/tag/v3.0.1

Restart Required: Yes

Instructions:

1. Update OpenEXR to version 3.0.1 or later using your package manager. 2. Recompile any applications using OpenEXR against the updated library. 3. Restart affected services or applications.

🔧 Temporary Workarounds

Disable EXR file processing

all

Temporarily block or reject EXR image files in vulnerable applications.

# Configure application to reject .exr files
# Use file type filtering in web applications

Run with reduced privileges

linux

Execute vulnerable applications with minimal user permissions to limit damage.

sudo -u nobody ./vulnerable_app
chroot or containerize the application

🧯 If You Can't Patch

Implement strict input validation to reject malformed EXR files
Isolate vulnerable systems in network segments with no internet access

🔍 How to Verify

Check if Vulnerable:

Check OpenEXR version: `exrheader --version` or `ldconfig -p | grep OpenEXR`. If version is below 3.0.1, system is vulnerable.

Check Version:

exrheader --version 2>/dev/null || pkg-config --modversion OpenEXR

Verify Fix Applied:

Confirm OpenEXR version is 3.0.1 or higher: `exrheader --version | grep -q '3\.0\.1\|3\.[1-9]\|4\.' && echo 'Patched'`

📡 Detection & Monitoring

Log Indicators:

Application crashes with segmentation faults
Memory corruption errors in application logs
Unexpected process termination when processing image files

Network Indicators:

Unusual outbound connections from media processing applications
Large EXR file uploads to web applications

SIEM Query:

source="application.log" AND ("segmentation fault" OR "heap corruption" OR "buffer overflow") AND process="*exr*"

📊 Metadata

CVE ID: CVE-2021-23169

CVSS v3 Score: 8.8 (HIGH)

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

CWE: CWE-787

Published: June 8, 2021

Last Updated: November 21, 2024

🔗 References

https://bugzilla.redhat.com/show_bug.cgi?id=1947612 Issue Tracking,Third Party Advisory
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/4KYNJSMVA6YJY5NMKDZ5SAISKZG2KCKC/
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/BXFLD4ZAXKAIWO6ZPBCQEEDZB5IG676K/
https://security.gentoo.org/glsa/202210-31 Third Party Advisory
https://bugzilla.redhat.com/show_bug.cgi?id=1947612 Issue Tracking,Third Party Advisory
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/4KYNJSMVA6YJY5NMKDZ5SAISKZG2KCKC/
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/BXFLD4ZAXKAIWO6ZPBCQEEDZB5IG676K/
https://security.gentoo.org/glsa/202210-31 Third Party Advisory

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