[qwertyuiop924]

For B) All hash table implementations are vulnerable to this kind of attack. However, some kinds of chaining are less vulnerable. In particular, balanced binary tree chaining would make the worst-case lookup (and insertion?) time complexity O(log n), which is a significant improvement over probing or linked list chaining. The tricks mentioned in the other comments above also improve things, by making such an event less likely.

As for A), no. No, JSON handling doesn't need hashtables. Since your app will only look at certain values in the JSON, you can simply ignore all the other values, and dump the values in an object/struct of your choosing. It wouldn't even be all that hard to write, provided you know how to write a parser...

[nickpsecurity]

Since your app will only look at certain values in the JSON, you can simply ignore all the other values, and dump the values in an object/struct of your choosing. It wouldn't even be all that hard to write, provided you know how to write a parser..."

That's what I was thinking. Never seen verified parsers or generators requiring these things. So I figured it was an unnecessary requirement bringing in its own security issue.

[vidarh]

A large part of the problem is that people want to be able to "just" de-serialize a chunk of JSON into a suitable generic structure they can then "just" de-reference as a suitable tree of dictionaries and arrays. It'd be fantastic to see easier-to-use patterns to discourage resorting to this, but it's very hard to beat for simplicity.