# scanf Bypasses

Sometimes you want `scanf` to not read anything, but continue standard execution. By this I mean that it **takes** your input, but it doesn't store it in memory, leaving the stack or heap untouched.

This might be because you have a sequential or iterative OOB write, but there is a canary in the way. Alternatively, the location you are writing to is **uninitialized** but the data gets printed back and you want to leak pointers this way (e.g. [Control Room](https://app.hackthebox.com/challenges/Control%2520Room) on Hack The Box).

So, here are a few inputs for different specifiers that help bypass this! Please do let me know of any more.

<table><thead><tr><th width="378">Scanf Specifier</th><th>Bypass</th></tr></thead><tbody><tr><td><code>%d</code>, <code>%ld</code></td><td>negative sign <code>-</code></td></tr><tr><td><code>%f</code>, <code>%lf</code></td><td>decimal point/full stop <code>.</code></td></tr><tr><td></td><td></td></tr></tbody></table>


---

# Agent Instructions: Querying This Documentation

If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question.

Perform an HTTP GET request on the current page URL with the `ask` query parameter:

```
GET https://ir0nstone.gitbook.io/notes/misc/scanf-bypasses.md?ask=<question>
```

The question should be specific, self-contained, and written in natural language.
The response will contain a direct answer to the question and relevant excerpts and sources from the documentation.

Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.