hacktricks/reversing-and-exploiting/linux-exploiting-basic-esp/arbitrary-write-2-exec/aw2exec-__malloc_hook.md

# AW2Exec - \_\_malloc\_hook

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## **Malloc Hook**

As you can [Official GNU site](https://www.gnu.org/software/libc/manual/html\_node/Hooks-for-Malloc.html), the variable **`__malloc_hook`** is a pointer pointing to the **address of a function that will be called** whenever `malloc()` is called **stored in the data section of the libc library**. Therefore, if this address is overwritten with a **One Gadget** for example and `malloc` is called, the **One Gadget will be called**.

To call malloc it's possible to wait for the program to call it or by **calling `printf("%10000$c")`** which allocates too bytes many making `libc`  calling malloc to allocate them in the heap.

More info about One Gadget in:

{% content-ref url="../one-gadget.md" %}
[one-gadget.md](../one-gadget.md)
{% endcontent-ref %}

{% hint style="danger" %}
Note that hooks are **disabled for GLIBC >= 2.34**. There are other techniques that can be used on modern GLIBC versions. See [https://github.com/nobodyisnobody/docs/blob/main/code.execution.on.last.libc/README.md](https://github.com/nobodyisnobody/docs/blob/main/code.execution.on.last.libc/README.md).
{% endhint %}

## References

* [https://ir0nstone.gitbook.io/notes/types/stack/one-gadgets-and-malloc-hook](https://ir0nstone.gitbook.io/notes/types/stack/one-gadgets-and-malloc-hook)
* [https://github.com/nobodyisnobody/docs/blob/main/code.execution.on.last.libc/README.md](https://github.com/nobodyisnobody/docs/blob/main/code.execution.on.last.libc/README.md)

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Learn & practice GCP Hacking: <img src="/.gitbook/assets/grte.png" alt="" data-size="line">[**HackTricks Training GCP Red Team Expert (GRTE)**<img src="/.gitbook/assets/grte.png" alt="" data-size="line">](https://training.hacktricks.xyz/courses/grte)

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