CVE-2022-40159 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
CVE-2022-40160
This is a major security flaw. The parser should be given an empty string as input to avoid this.
User Input Data Validation
One way to validate user input data is using a regular expression. For example, the following regular expression will ensure that an input string does not contain the letter x:
/^[0-9]*\$/
The following regular expression would validate input data for properly formatted URLs:
/^https:\/\/([a-zA-Z0-9]+)/
XML Parsing Best Practices
XML parsing is the process of converting an XML document into a data structure, typically a tree-structured collection of nodes.
There are many ways to parse an XML document and the best way to parse is usually dependent on the task. The easiest way to parse is if there is just a single root node in the beginning of the XML file. This can be done by using a recursive-descent parser, which starts with one element in the beginning of the document and continues downward until it reaches another element. This type of parser will never run out of stack space during its execution because it never needs to allocate more than one level deep. The recursive-descent parser would only need to use one stack space in this scenario.
On the other hand, if there are multiple top-level elements present at the beginning of an XML file, then you can use a context-sensitive parsing algorithm that parses only where it is needed rather than recursively following all nodes down through all levels. This type of parser will also not run out of stack space as long as there isn’t any nesting that goes deeper than two layers deep or so for each context-sensitive parser that is being used for this kind of parsing task.
So now let’s see how you could use these best practices to validate input data before parsing:
1) Validate user input data: If your application has users inputting some text into forms, make sure they entered text
Timeline
Published on: 10/06/2022 18:16:00 UTC
Last modified on: 10/07/2022 19:04:00 UTC