CVE-2019-12068 - Loop with Unreachable Exit Condition ('Infinite Loop')

Severity

38%

Complexity

20%

Confidentiality

23%

In QEMU 1:4.1-1, 1:2.1+dfsg-12+deb8u6, 1:2.8+dfsg-6+deb9u8, 1:3.1+dfsg-8~deb10u1, 1:3.1+dfsg-8+deb10u2, and 1:2.1+dfsg-12+deb8u12 (fixed), when executing script in lsi_execute_script(), the LSI scsi adapter emulator advances 's->dsp' index to read next opcode. This can lead to an infinite loop if the next opcode is empty. Move the existing loop exit after 10k iterations so that it covers no-op opcodes as well.

In QEMU 1:4.1-1, 1:2.1+dfsg-12+deb8u6, 1:2.8+dfsg-6+deb9u8, 1:3.1+dfsg-8~deb10u1, 1:3.1+dfsg-8+deb10u2, and 1:2.1+dfsg-12+deb8u12 (fixed), when executing script in lsi_execute_script(), the LSI scsi adapter emulator advances 's->dsp' index to read next opcode. This can lead to an infinite loop if the next opcode is empty. Move the existing loop exit after 10k iterations so that it covers no-op opcodes as well.

CVSS 3.1 Base Score 3.8. CVSS Attack Vector: local. CVSS Attack Complexity: low. CVSS Vector: (CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:N/I:N/A:L).

CVSS 2.0 Base Score 2.1. CVSS Attack Vector: local. CVSS Attack Complexity: low. CVSS Vector: (AV:L/AC:L/Au:N/C:N/I:N/A:P).

Demo Examples

Loop with Unreachable Exit Condition ('Infinite Loop')

CWE-835

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 failure

However, 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 failure

Loop with Unreachable Exit Condition ('Infinite Loop')

CWE-835

For 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 true
isReorder = 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 variable
return isReorder;

Overview

First reported 5 years ago

2019-09-24 20:15:00

Last updated 4 years ago

2020-04-28 13:15:00

Affected Software

Canonical Ubuntu Linux 14.04 ESM Edition

14.04

Canonical Ubuntu Linux 16.04 LTS (Long-Term Support)

16.04

Canonical Ubuntu Linux 18.04 LTS Edition

18.04

Canonical Ubuntu Linux 19.04

19.04

Canonical Ubuntu Linux 19.10

19.10

openSUSE Leap 15.0

15.0

OpenSUSE Leap 15.1

15.1

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