CWE-835: Loop with Unreachable Exit Condition ('Infinite Loop')

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Description

The product contains an iteration or loop with an exit condition that cannot be reached, i.e., an infinite loop.

Extended Description

N/A

ThreatScore

Threat Mapped score: 0.0

Industry: Finiancial

Threat priority: Unclassified

Observed Examples (CVEs)

Related Attack Patterns (CAPEC)

N/A

Attack TTPs

N/A

Modes of Introduction

Phase Note
None listed.

Common Consequences

Potential Mitigations

Applicable Platforms

Demonstrative Examples

Intro: 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.

Body: 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.

int processMessagesFromServer(char *hostaddr, int port) { ... int servsock; int connected; struct sockaddr_in servaddr; // create socket to connect to server servsock = socket( AF_INET, SOCK_STREAM, 0); memset( &servaddr, 0, sizeof(servaddr)); servaddr.sin_family = AF_INET; servaddr.sin_port = htons(port); servaddr.sin_addr.s_addr = inet_addr(hostaddr); do { // establish connection to server connected = connect(servsock, (struct sockaddr *)&servaddr, sizeof(servaddr)); // if connected then read and process messages from server if (connected > -1) { // read and process messages ... } // keep trying to establish connection to the server } while (connected < 0); // close socket and return success or failure ... }

Intro: For this example, the method isReorderNeeded is 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.

Body: 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.

public boolean isReorderNeeded(String bookISBN, int rateSold) { boolean isReorder = false; int minimumCount = 10; int days = 0; // get inventory count for book int inventoryCount = inventory.getIventoryCount(bookISBN); // find number of days until inventory count reaches minimum while (inventoryCount > minimumCount) { inventoryCount = inventoryCount - rateSold; days++; } // if number of days within reorder timeframe // set reorder return boolean to true if (days > 0 && days < 5) { isReorder = true; } return isReorder; }

Notes

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