CVE-2020-18831
📋 TL;DR
A buffer overflow vulnerability in Exiv2's PNG processing allows remote attackers to cause denial of service or potentially execute arbitrary code by providing a specially crafted PNG file. This affects applications that use Exiv2 to process PNG metadata, including image viewers, web applications, and file management tools. The vulnerability is triggered when parsing tEXt chunks in PNG files.
💻 Affected Systems
- Exiv2
- Applications using Exiv2 library
📦 What is this software?
Exiv2 by Exiv2
⚠️ Risk & Real-World Impact
Worst Case
Remote code execution leading to complete system compromise if the buffer overflow can be controlled to execute arbitrary code.
Likely Case
Denial of service through application crash when processing malicious PNG files, potentially disrupting image processing services.
If Mitigated
Application crash with no further impact if exploit attempts fail or are contained by security controls.
🎯 Exploit Status
Exploitation requires crafting a malicious PNG file with specific tEXt chunk structure to trigger the buffer overflow.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Exiv2 0.27.2 and later
Vendor Advisory: https://github.com/Exiv2/exiv2/issues/828
Restart Required: Yes
Instructions:
1. Download Exiv2 0.27.2 or later from https://www.exiv2.org/download.html
2. Compile and install the updated version
3. Recompile any applications using Exiv2 against the patched library
4. Restart affected services
🔧 Temporary Workarounds
Disable PNG processing
allConfigure applications to avoid processing PNG files or disable Exiv2 PNG metadata extraction
Application-specific configuration required
Input validation
allImplement file type validation and size limits for PNG uploads
Implement in application code
🧯 If You Can't Patch
- Implement strict file upload validation rejecting PNG files from untrusted sources
- Run Exiv2 in sandboxed/containerized environments with limited privileges
🔍 How to Verify
Check if Vulnerable:
Check Exiv2 version: exiv2 --version | grep -i versionCheck Version:
exiv2 --versionVerify Fix Applied:
Verify version is 0.27.2 or higher: exiv2 --version📡 Detection & Monitoring
Log Indicators:
- Application crashes when processing PNG files
- Segmentation faults in Exiv2 processes
Network Indicators:
- Unusual PNG file uploads to web applications
- Multiple failed PNG processing attempts
SIEM Query:
source="application.log" AND ("segmentation fault" OR "buffer overflow") AND "exiv2"