CVE-2021-26259
📋 TL;DR
CVE-2021-26259 is a heap buffer overflow vulnerability in htmldoc's render_table_row() function that could allow attackers to execute arbitrary code or cause denial of service. This affects systems running htmldoc v1.9.12 when processing malicious HTML documents containing specially crafted tables.
💻 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 crashes when processing malicious documents.
If Mitigated
Limited impact if htmldoc runs with minimal privileges and in isolated environments.
🎯 Exploit Status
Exploitation requires the victim to process a malicious HTML document. Proof-of-concept code is available in the GitHub issue.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Fixed in commit 0ddab26a542c74770317b622e985c52430092ba5 and later versions
Vendor Advisory: https://github.com/michaelrsweet/htmldoc/commit/0ddab26a542c74770317b622e985c52430092ba5
Restart Required: No
Instructions:
1. Update htmldoc to the latest version from the official repository. 2. Recompile if using source code. 3. Replace existing htmldoc binary with the patched version.
🔧 Temporary Workarounds
Disable table processing
allAvoid processing HTML documents containing tables with htmldoc
Run with reduced privileges
linuxExecute htmldoc with minimal user privileges to limit potential damage
sudo -u nobody htmldoc document.html
🧯 If You Can't Patch
- Restrict htmldoc usage to trusted documents only
- Implement sandboxing or containerization for htmldoc processes
🔍 How to Verify
Check if Vulnerable:
Check htmldoc version: htmldoc --version. If output shows v1.9.12, the system is vulnerable.Check Version:
htmldoc --versionVerify Fix Applied:
Verify version is newer than v1.9.12 or check if commit 0ddab26a542c74770317b622e985c52430092ba5 is included in the build.📡 Detection & Monitoring
Log Indicators:
- Segmentation fault or crash logs from htmldoc process
- Unusual memory allocation patterns
Network Indicators:
- Not applicable - this is a local file processing vulnerability
SIEM Query:
Process:name="htmldoc" AND (EventID="1000" OR Signal="SIGSEGV")