CVE-2021-39582
📋 TL;DR
A heap buffer overflow vulnerability in swftools allows attackers to execute arbitrary code by exploiting the swf_GetPlaceObject() function. This affects all users of swftools up to version 20200710 who process untrusted SWF files. Successful exploitation could lead to complete system compromise.
💻 Affected Systems
- swftools
📦 What is this software?
Swftools by Swftools
⚠️ Risk & Real-World Impact
Worst Case
Remote code execution with full system compromise, allowing attacker to install malware, exfiltrate data, or pivot to other systems.
Likely Case
Application crash leading to denial of service, with potential for limited code execution in constrained environments.
If Mitigated
Application crash without code execution if memory protections like ASLR are effective.
🎯 Exploit Status
Proof of concept available in GitHub issue. Exploitation requires crafting specific SWF file to trigger overflow.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Version after 20200710
Vendor Advisory: https://github.com/matthiaskramm/swftools/issues/122
Restart Required: No
Instructions:
1. Update swftools to latest version from official repository. 2. Recompile if using source. 3. Replace existing binaries with patched version.
🔧 Temporary Workarounds
Disable SWF processing
linuxTemporarily disable swftools processing of untrusted SWF files
# Remove execute permissions from swftools binaries
chmod -x /usr/bin/swftools
Input validation
allImplement strict validation of SWF files before processing
🧯 If You Can't Patch
- Isolate swftools to dedicated VM with no network access
- Implement application allowlisting to prevent unauthorized swftools execution
🔍 How to Verify
Check if Vulnerable:
Check swftools version: swftools --version | grep -i versionCheck Version:
swftools --versionVerify Fix Applied:
Verify version is newer than 20200710 and test with known safe SWF files📡 Detection & Monitoring
Log Indicators:
- Segmentation fault errors in system logs
- Abnormal process termination of swftools
Network Indicators:
- Unusual outbound connections from swftools process
SIEM Query:
process_name:swftools AND (event_id:1000 OR signal:SIGSEGV)