CVE-2020-27778
📋 TL;DR
CVE-2020-27778 is a vulnerability in Poppler's pdftohtml utility that allows remote attackers to cause denial of service through a malicious PDF file. When processed, the application crashes, disrupting PDF-to-HTML conversion services. This affects systems running vulnerable versions of Poppler with pdftohtml enabled.
💻 Affected Systems
- Poppler
- pdftohtml
📦 What is this software?
Poppler by Freedesktop
⚠️ Risk & Real-World Impact
Worst Case
Complete denial of service for PDF processing services, potentially disrupting business workflows that rely on automated PDF-to-HTML conversion.
Likely Case
Application crashes when processing malicious PDFs, causing temporary service disruption until the process restarts.
If Mitigated
Minimal impact with proper input validation and process isolation; crashes are contained to individual conversion jobs.
🎯 Exploit Status
Exploitation requires providing a malicious PDF file to the pdftohtml utility, which is straightforward for attackers.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Poppler 20.12.1 and later
Vendor Advisory: https://bugzilla.redhat.com/show_bug.cgi?id=1900712
Restart Required: No
Instructions:
1. Update Poppler to version 20.12.1 or later using your package manager. 2. For Red Hat/CentOS: 'yum update poppler'. 3. For Debian/Ubuntu: 'apt-get update && apt-get install poppler-utils'. 4. Verify the update with 'pdftohtml --version'.
🔧 Temporary Workarounds
Disable pdftohtml
linuxRemove or disable the pdftohtml utility if not required
sudo apt-get remove poppler-utils
sudo yum remove poppler-utils
Input validation
allImplement PDF file validation before processing with pdftohtml
🧯 If You Can't Patch
- Isolate pdftohtml processes in containers with resource limits to contain crashes
- Implement monitoring and automatic restart for pdftohtml processes
🔍 How to Verify
Check if Vulnerable:
Check Poppler version: 'pdftohtml --version' or 'poppler --version'. If version is earlier than 20.12.1, system is vulnerable.Check Version:
pdftohtml --versionVerify Fix Applied:
Confirm version is 20.12.1 or later: 'pdftohtml --version | grep -E "20\.12\.1|2[1-9]|\d{2,}\.\d+\.\d+"'📡 Detection & Monitoring
Log Indicators:
- Segmentation fault errors in system logs
- pdftohtml process crashes
- Abnormal termination of PDF processing jobs
Network Indicators:
- Multiple failed PDF uploads to conversion services
- Unusual PDF file patterns in network traffic
SIEM Query:
process.name="pdftohtml" AND (event.action="segmentation_fault" OR event.outcome="failure")