CVE-2024-12720
📋 TL;DR
A Regular Expression Denial of Service (ReDoS) vulnerability exists in the huggingface/transformers library's tokenization_nougat_fast.py file. The post_process_single() function uses a regex that can cause exponential backtracking with specially crafted input, leading to high CPU consumption and potential application downtime. Anyone using huggingface/transformers version 4.46.3 is affected.
💻 Affected Systems
- huggingface/transformers
📦 What is this software?
Transformers by Huggingface
⚠️ Risk & Real-World Impact
Worst Case
Complete application unavailability due to CPU exhaustion, causing extended service downtime and potential cascading failures in dependent systems.
Likely Case
Degraded application performance with high CPU spikes, leading to slow response times and potential temporary unavailability under load.
If Mitigated
Minimal performance impact with proper input validation and rate limiting in place.
🎯 Exploit Status
Exploitation requires crafting specific input patterns to trigger regex backtracking. No authentication bypass needed if the vulnerable endpoint is accessible.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: v4.47.0 or apply the specific commit
Vendor Advisory: https://github.com/huggingface/transformers/commit/deac971c469bcbb182c2e52da0b82fb3bf54cccf
Restart Required: No
Instructions:
1. Update huggingface/transformers to version 4.47.0 or later using pip install --upgrade transformers. 2. Alternatively, apply the specific commit deac971c469bcbb182c2e52da0b82fb3bf54cccf if using a custom build.
🔧 Temporary Workarounds
Input Validation and Sanitization
allImplement strict input validation to reject or sanitize potentially malicious patterns before they reach the vulnerable regex.
Rate Limiting
allImplement rate limiting on endpoints that process user input to prevent mass exploitation attempts.
🧯 If You Can't Patch
- Disable or restrict access to endpoints using the Nougat tokenizer functionality.
- Implement Web Application Firewall (WAF) rules to detect and block patterns that could trigger ReDoS.
🔍 How to Verify
Check if Vulnerable:
Check if transformers version is 4.46.3 and if the application uses Nougat tokenizer functionality.Check Version:
python -c "import transformers; print(transformers.__version__)"Verify Fix Applied:
Verify transformers version is 4.47.0 or later, or confirm the commit deac971c469bcbb182c2e52da0b82fb3bf54cccf is applied.📡 Detection & Monitoring
Log Indicators:
- Unusually high CPU usage spikes
- Increased processing time for tokenization requests
- Application timeouts or crashes
Network Indicators:
- Multiple requests with similar patterns to the same endpoint
- Unusual traffic spikes to tokenization endpoints
SIEM Query:
source="application_logs" AND (message="*CPU spike*" OR message="*timeout*" OR message="*tokenization*" AND message="*slow*")