CVE-2021-34119
📋 TL;DR
CVE-2021-34119 is a heap-based buffer overflow vulnerability in HTMLDOC's parse_paragraph function that allows remote code execution or denial of service when processing malicious files. This affects systems running HTMLDOC 1.9.12 or earlier versions that parse untrusted input files. Users who convert HTML to PDF using HTMLDOC with external file sources are at risk.
💻 Affected Systems
- HTMLDOC
📦 What is this software?
Htmldoc by Htmldoc Project
⚠️ Risk & Real-World Impact
Worst Case
Remote code execution with the privileges of the HTMLDOC process, potentially leading to full system compromise.
Likely Case
Denial of service through application crash when processing crafted files.
If Mitigated
Limited impact if HTMLDOC runs with minimal privileges and only processes trusted files.
🎯 Exploit Status
Proof of concept demonstrates crash; weaponization for RCE would require additional exploit development.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: 1.9.13 and later
Vendor Advisory: https://github.com/michaelrsweet/htmldoc/security/advisories
Restart Required: No
Instructions:
1. Download HTMLDOC 1.9.13 or later from official repository. 2. Compile and install following platform-specific build instructions. 3. Replace existing HTMLDOC binary with patched version.
🔧 Temporary Workarounds
Restrict file processing
allLimit HTMLDOC to process only trusted, validated files from known sources.
Run with reduced privileges
linuxExecute HTMLDOC with minimal user privileges to limit potential damage from exploitation.
sudo -u nobody htmldoc [options]
🧯 If You Can't Patch
- Implement strict input validation for all files processed by HTMLDOC
- Isolate HTMLDOC execution in container or sandbox environment
🔍 How to Verify
Check if Vulnerable:
Check HTMLDOC version: htmldoc --version. If version is 1.9.12 or earlier, system is vulnerable.Check Version:
htmldoc --versionVerify Fix Applied:
After patching, verify version is 1.9.13 or later: htmldoc --version📡 Detection & Monitoring
Log Indicators:
- HTMLDOC process crashes
- Abnormal memory usage patterns
- Unexpected file processing errors
Network Indicators:
- Unusual file uploads to HTMLDOC processing endpoints
- Exploit kit traffic patterns
SIEM Query:
process_name:"htmldoc" AND (event_type:"crash" OR memory_usage:"high")