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In systemd 223 through 235, a remote DNS server can respond with a custom crafted DNS NSEC resource record to trigger an infinite loop in the dns_packet_read_type_window() function of the 'systemd-resolved' service and cause a DoS of the affected service.
In systemd 223 through 235, a remote DNS server can respond with a custom crafted DNS NSEC resource record to trigger an infinite loop in the dns_packet_read_type_window() function of the 'systemd-resolved' service and cause a DoS of the affected service.
CVSS 3.0 Base Score 7.5. CVSS Attack Vector: network. CVSS Attack Complexity: low. CVSS Vector: (CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H).
CVSS 2.0 Base Score 5. CVSS Attack Vector: network. CVSS Attack Complexity: low. CVSS Vector: (AV:N/AC:L/Au:N/C:N/I:N/A:P).
In the following code the method processMessagesFromServer attempts to establish a connection to a server and read and process messages from the server. The method uses a do/while loop to continue trying to establish the connection to the server when an attempt fails.
}
...// create socket to connect to server
}// establish connection to server// if connected then read and process messages from server
...// read and process messages// keep trying to establish connection to the server// close socket and return success or failureHowever, this will create an infinite loop if the server does not respond. This infinite loop will consume system resources and can be used to create a denial of service attack. To resolve this a counter should be used to limit the number of attempts to establish a connection to the server, as in the following code.
}
...// initialize number of attempts counter
}// establish connection to server// increment counter// if connected then read and process messages from server
...// read and process messages// keep trying to establish connection to the server// up to a maximum number of attempts// close socket and return success or failureFor this example the method isReorderNeeded as part of a bookstore application that determines if a particular book needs to be reordered based on the current inventory count and the rate at which the book is being sold.
}
return isReorder;// get inventory count for book// find number of days until inventory count reaches minimum
days++;// if number of days within reorder timeframe// set reorder return boolean to trueisReorder = true;However, the while loop will become an infinite loop if the rateSold input parameter has a value of zero since the inventoryCount will never fall below the minimumCount. In this case the input parameter should be validated to ensure that a value of zero does not cause an infinite loop,as in the following code.
}
...// validate rateSold variablereturn isReorder;ExploitPedia is constantly evolving. Sign up to receive a notification when we release additional functionality.
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