CVE-2022-40161 JXPath is vulnerable to DOS attacks if the parser is running on user supplied input.
There are two ways this can happen. The first is when input data is supplied that the parser doesn’t understand, such as an illegal character. The second way is when the parser is supplied with data that the parser already understands. For example, if the parser is given an XML document that contains a start tag with an ID attribute, then this already understood data will cause a stack overflow. The same applies if the parser is given an XML document that contains an end tag with an ID attribute. Therefore, it is important to always validate input data before parsing. Some best practices for validation include: - Validation of user input data - Validation of data inside data structures
Refrain from standard input validation
This is a very common mistake that people make when developing applications. You should refrain from standard input validation for the following reasons:
- It can be difficult to implement - Validation of user input data is better done at the server level, instead of on the client side
- It can be difficult to determine whether the validation error was due to an error in the application or if it is a bug in the parser
Stack overflow in the parsing stage
A stack overflow occurs when the parser is unable to allocate memory. After the parser allocates memory and starts parsing, it will continue attempting to process input data until it runs out of memory. The stack overflow happens when the parser encounters an invalid value that can’t be processed. This can happen if the input data contains illegal characters or if the parser is provided with data that it already knows how to process.
The only way to prevent a stack overflow in your code is by validating all input data before using it as a parameter for parsing. Some best practices for validation include: - Validation of user input data - Validation of data inside data structures
The XML parser doesn’t understand input data :
The XML parser doesn’t understand input data until the end tag is recognized. This means that if you have a document with an opening tag, then the parser will not be able to parse your XML until it finds a closing tag. What happens when you provide the parser with input data that it doesn’t understand? It crashes and presents an error message!
User Input Data Validation
User input data validation is very important. One way to ensure that user input data is validated is by using a regular expression. For example, if you are trying to validate an email address, you could use the regex [a-zA-Z0-9]+\.[a-zA-Z0-9]+ as your validation method.
Regular expressions are hard to understand and they don't always work well in real time applications-- especially when they have to be applied in a large number of places. They also require many different resources such as memory, processor power, and time (it takes on average 10 minutes for a regular expression search engine like GrepWords). However, no other validation method can match the speed at which a regular expression search engine like GrepWords works.
Timeline
Published on: 10/06/2022 18:16:00 UTC
Last modified on: 10/07/2022 18:55:00 UTC