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A shortcoming in the HMEF package of poi-scratchpad (Apache POI) allows an attacker to cause an Out of Memory exception. This package is used to read TNEF files (Microsoft Outlook and Microsoft Exchange Server). If an application uses poi-scratchpad to parse TNEF files and the application allows untrusted users to supply them, then a carefully crafted file can cause an Out of Memory exception. This issue affects poi-scratchpad version 5.2.0 and prior versions. Users are recommended to upgrade to poi-scratchpad 5.2.1.
CVSS 3.1 Base Score 5.5. CVSS Attack Vector: local. CVSS Attack Complexity: low. CVSS Vector: (CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H).
CVSS 2.0 Base Score 4.3. CVSS Attack Vector: network. CVSS Attack Complexity: medium. CVSS Vector: (AV:N/AC:M/Au:N/C:N/I:N/A:P).
This code allocates a socket and forks each time it receives a new connection.
}pid = fork();The program does not track how many connections have been made, and it does not limit the number of connections. Because forking is a relatively expensive operation, an attacker would be able to cause the system to run out of CPU, processes, or memory by making a large number of connections. Alternatively, an attacker could consume all available connections, preventing others from accessing the system remotely.
In the following example a server socket connection is used to accept a request to store data on the local file system using a specified filename. The method openSocketConnection establishes a server socket to accept requests from a client. When a client establishes a connection to this service the getNextMessage method is first used to retrieve from the socket the name of the file to store the data, the openFileToWrite method will validate the filename and open a file to write to on the local file system. The getNextMessage is then used within a while loop to continuously read data from the socket and output the data to the file until there is no longer any data from the socket.
}
closeSocket(socket);return(FAIL);
closeFile();
}
break;This example creates a situation where data can be dumped to a file on the local file system without any limits on the size of the file. This could potentially exhaust file or disk resources and/or limit other clients' ability to access the service.
In the following example, the processMessage method receives a two dimensional character array containing the message to be processed. The two-dimensional character array contains the length of the message in the first character array and the message body in the second character array. The getMessageLength method retrieves the integer value of the length from the first character array. After validating that the message length is greater than zero, the body character array pointer points to the start of the second character array of the two-dimensional character array and memory is allocated for the new body character array.
}/* process message accepts a two-dimensional character array of the form [length][body] containing the message to be processed */
}return(SUCCESS);return(FAIL);This example creates a situation where the length of the body character array can be very large and will consume excessive memory, exhausting system resources. This can be avoided by restricting the length of the second character array with a maximum length check
Also, consider changing the type from 'int' to 'unsigned int', so that you are always guaranteed that the number is positive. This might not be possible if the protocol specifically requires allowing negative values, or if you cannot control the return value from getMessageLength(), but it could simplify the check to ensure the input is positive, and eliminate other errors such as signed-to-unsigned conversion errors (CWE-195) that may occur elsewhere in the code.
if ((length > 0) && (length < MAX_LENGTH)) {...}In the following example, a server object creates a server socket and accepts client connections to the socket. For every client connection to the socket a separate thread object is generated using the ClientSocketThread class that handles request made by the client through the socket.
}
} catch (IOException ex) {...}serverSocket.close();t.start();In this example there is no limit to the number of client connections and client threads that are created. Allowing an unlimited number of client connections and threads could potentially overwhelm the system and system resources.
The server should limit the number of client connections and the client threads that are created. This can be easily done by creating a thread pool object that limits the number of threads that are generated.
}
} catch (IOException ex) {...}serverSocket.close();pool.execute(t);Here the problem is that every time a connection is made, more memory is allocated. So if one just opened up more and more connections, eventually the machine would run out of memory.
}return foo;free(foo);endConnection(foo)foo=connection();This example demonstrates a shopping interaction in which the user is free to specify the quantity of items to be purchased and a total is calculated.
...The user has no control over the price variable, however the code does not prevent a negative value from being specified for quantity. If an attacker were to provide a negative value, then the user would have their account credited instead of debited.
This example asks the user for a height and width of an m X n game board with a maximum dimension of 100 squares.
.../* board dimensions */die("No integer passed: Die evil hacker!\n");die("No integer passed: Die evil hacker!\n");die("Value too large: Die evil hacker!\n");While this code checks to make sure the user cannot specify large, positive integers and consume too much memory, it does not check for negative values supplied by the user. As a result, an attacker can perform a resource consumption (CWE-400) attack against this program by specifying two, large negative values that will not overflow, resulting in a very large memory allocation (CWE-789) and possibly a system crash. Alternatively, an attacker can provide very large negative values which will cause an integer overflow (CWE-190) and unexpected behavior will follow depending on how the values are treated in the remainder of the program.
The following example shows a PHP application in which the programmer attempts to display a user's birthday and homepage.
echo "Birthday: $birthday<br>Homepage: <a href=$homepage>click here</a>"The programmer intended for $birthday to be in a date format and $homepage to be a valid URL. However, since the values are derived from an HTTP request, if an attacker can trick a victim into clicking a crafted URL with <script> tags providing the values for birthday and / or homepage, then the script will run on the client's browser when the web server echoes the content. Notice that even if the programmer were to defend the $birthday variable by restricting input to integers and dashes, it would still be possible for an attacker to provide a string of the form:
2009-01-09--If this data were used in a SQL statement, it would treat the remainder of the statement as a comment. The comment could disable other security-related logic in the statement. In this case, encoding combined with input validation would be a more useful protection mechanism.
Furthermore, an XSS (CWE-79) attack or SQL injection (CWE-89) are just a few of the potential consequences when input validation is not used. Depending on the context of the code, CRLF Injection (CWE-93), Argument Injection (CWE-88), or Command Injection (CWE-77) may also be possible.
This function attempts to extract a pair of numbers from a user-supplied string.
}
die("Did not specify integer value. Die evil hacker!\n");/* proceed assuming n and m are initialized correctly */This code attempts to extract two integer values out of a formatted, user-supplied input. However, if an attacker were to provide an input of the form:
123:then only the m variable will be initialized. Subsequent use of n may result in the use of an uninitialized variable (CWE-457).
The following example takes a user-supplied value to allocate an array of objects and then operates on the array.
}list[0] = new Widget();die("Negative value supplied for list size, die evil hacker!");This example attempts to build a list from a user-specified value, and even checks to ensure a non-negative value is supplied. If, however, a 0 value is provided, the code will build an array of size 0 and then try to store a new Widget in the first location, causing an exception to be thrown.
This application has registered to handle a URL when sent an intent:
}......
}
}int length = URL.length();...The application assumes the URL will always be included in the intent. When the URL is not present, the call to getStringExtra() will return null, thus causing a null pointer exception when length() is called.
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