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How the CVE Works:
The vulnerability (CVE-2025-XXXX) in vLLM’s OpenAI-compatible server allows attackers to trigger a denial-of-service (DoS) condition by sending a maliciously crafted invalid regex pattern in structured output requests. When the server processes this regex, it fails to handle the malformed input gracefully, causing the service to crash. This occurs due to insufficient input validation in the regex parsing logic, similar to GHSA-6qc9-v4r8-22xg but affecting regex instead of JSON schema. The issue stems from an uncaught exception when evaluating the regex, leading to abrupt termination of the server process.
DailyCVE Form:
Platform: vLLM
Version: < 0.4.0
Vulnerability: Regex DoS
Severity: Moderate
Date: May 28, 2025
Prediction: Patch expected by June 10, 2025
What Undercode Say:
Exploitation:
1. Craft a request with a malformed regex:
import openai
openai.api_key = "sk-..."
response = openai.ChatCompletion.create(
model="vllm",
messages=[{"role": "user", "content": "..."}],
regex_pattern="([a-z]+)$" Catastrophic backtracking trigger
)
2. Send repeated requests to degrade service availability.
Mitigation:
- Update vLLM to the patched version once released.
2. Implement regex input validation:
import re def validate_regex(pattern): try: re.compile(pattern) return True except re.error: return False
3. Deploy rate-limiting to prevent abuse.
Detection:
Check logs for repeated crashes with regex-related errors:
grep -i "regex error" /var/log/vllm/server.log
Temporary Workaround:
Disable structured output regex support in config:
vllm-config.yaml disable_structured_regex: true
Analytics:
- Attack Vector: Network-exploitable
- Complexity: Low
- Privileges Required: None
- User Interaction: None
- CVSS Score: 5.3 (Medium)
References:
Sources:
Reported By: github.com
Extra Source Hub:
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