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Why “Apache Range Header DoS (CVE-2011-3192)” can be dangerous
This attack is performed by means of HTTP Range request header which allows the client to receive only specified parts of the requested content. The header contains a list of byte ranges of the content that should be returned in the response. The crucial fact is that for each of the byte ranges a separate copy of the requested resource must be created on the server, so when the attacker sends a malicious request with the Range header consisting of a large list of byte ranges it causes CPU and memory exhaustion resulting in denial of service (DoS).
How to fix “Apache Range Header DoS (CVE-2011-3192)”
The best solution for this problem is to update your Apache Server to 2.2.21 or newer. There are other technical approaches that can help mitigate this threat described in https://httpd.apache.org/security/CVE-2011-3192.txt.
Disallow Range and Request-Range headers.
How does ScanRepeat report “Apache Range Header DoS (CVE-2011-3192)”
ScanRepeat checks if there are fingerprints in response for requests.
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