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How the CVE Works
The vulnerability in `github.com/rs/cors` middleware arises when processing malicious CORS preflight requests containing an excessively long `Access-Control-Request-Headers` (ACRH) header with numerous commas. This triggers excessive heap allocations, leading to increased memory consumption and server load. Attackers exploit this by sending crafted requests, overwhelming the server and causing a denial of service (DoS). The issue stems from inefficient header parsing, allowing trivial abuse with minimal effort.
DailyCVE Form
Platform: `github.com/rs/cors`
Version: `<=1.10.0`
Vulnerability: `DoS via ACRH`
Severity: `Low`
Date: `2025-08-06`
Prediction: `Patch expected by 2025-08-20`
What Undercode Say
Analytics:
curl -H "Access-Control-Request-Headers: $(python3 -c 'print("A,"10000)')" http://target/api
// Example vulnerable CORS config handler := cors.Default().Handler(mux)
How Exploit:
1. Send crafted preflight request with oversized ACRH.
2. Trigger repeated heap allocations.
3. Exhaust server resources.
Protection from this CVE:
- Update to patched version.
- Limit header size.
- Disable CORS if unused.
Impact:
- Server resource exhaustion.
- Service degradation.
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Sources:
Reported By: github.com
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