CVE-2022-43357
📋 TL;DR
A stack overflow vulnerability in libsass's CompoundSelector::has_real_parent_ref function allows attackers to cause denial of service by crashing the application. This affects libsass (a C/C++ Sass compiler) and sassc (its command-line driver), potentially impacting any software using these libraries for Sass compilation.
💻 Affected Systems
- libsass
- sassc
📦 What is this software?
Libsass by Sass Lang
Sassc by Sass Lang
⚠️ Risk & Real-World Impact
Worst Case
Complete service disruption through application crash, potentially affecting web development pipelines or services that process user-provided Sass/SCSS files.
Likely Case
Denial of service through application crash when processing maliciously crafted Sass/SCSS files, disrupting compilation workflows.
If Mitigated
Limited impact if proper input validation and sandboxing are implemented, with crashes contained to isolated processes.
🎯 Exploit Status
Proof-of-concept exploit code is available in the GitHub issue. Exploitation requires the ability to submit malicious Sass/SCSS files for compilation.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: libsass versions after commit addressing issue #3177
Vendor Advisory: https://github.com/sass/libsass/issues/3177
Restart Required: Yes
Instructions:
1. Update libsass to a patched version from the official repository. 2. Rebuild any applications using libsass. 3. Update sassc if using the command-line tool. 4. Restart affected services.
🔧 Temporary Workarounds
Input Validation and Sanitization
allImplement strict validation of Sass/SCSS input files before passing to libsass compilation
Process Isolation
allRun libsass compilation in isolated containers or sandboxed environments to contain crashes
🧯 If You Can't Patch
- Implement network segmentation to isolate systems using vulnerable libsass versions
- Deploy application-level firewalls to block malicious Sass/SCSS file uploads
🔍 How to Verify
Check if Vulnerable:
Check libsass version: `sassc --version` or examine linked library version in applicationsCheck Version:
sassc --version # or check libsass library version in build configurationVerify Fix Applied:
Verify updated to libsass version after the fix commit for issue #3177📡 Detection & Monitoring
Log Indicators:
- Application crashes with segmentation faults during Sass compilation
- Unusual memory usage patterns in libsass processes
Network Indicators:
- Multiple failed compilation requests from single sources
- Unusual Sass/SCSS file upload patterns
SIEM Query:
process.name:"sassc" AND event.action:"crash" OR process.name:"libsass" AND memory.usage:>threshold