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[Bugfix] Allow single-label hostnames in URL validation #737

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[Bugfix] Allow single-label hostnames in URL validation #737

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1 change: 1 addition & 0 deletions src/vllm_router/utils.py
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Original file line number Diff line number Diff line change
Expand Up @@ -157,6 +157,7 @@ def validate_url(url: str) -> bool:
regex = re.compile(
r"^(http|https)://" # Protocol
r"(([a-zA-Z0-9_-]+\.)+[a-zA-Z]{2,}|" # Domain name
r"[a-zA-Z0-9_-]+|" # single-label
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@gemini-code-assist gemini-code-assist bot Oct 16, 2025

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This regex for single-label hostnames is too permissive. It allows hostnames that start or end with a hyphen (e.g., -host or host-), which is invalid according to RFCs 952 and 1123. This could potentially lead to security vulnerabilities like Server-Side Request Forgery (SSRF).

Additionally, this general pattern makes the localhost alternative on the next line redundant. It's better to have specific patterns like localhost come before more general ones.

For security and correctness, please use a stricter pattern. Note that the multi-label domain regex on line 159 has a similar vulnerability and should also be considered for an update.

Suggested change
r"[a-zA-Z0-9_-]+|" # single-label
r"(?!-)[a-zA-Z0-9_-]+(?<!-)|" # single-label

r"localhost|" # Or localhost
r"\d{1,3}(\.\d{1,3}){3})" # Or IPv4 address
r"(:\d+)?" # Optional port
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