[shakna]

Format string attacks have occurred in the wild. [0]

> Originally thought harmless, format string exploits can be used to crash a program or to execute harmful code.

They are not the same as puts. Puts can allow you to potentially read memory.

A format string attack can allow you to write to memory.

[0] https://en.wikipedia.org/wiki/Uncontrolled_format_string

[cozzyd]

Yes if the attacker has control of the string (like if you do printf(getenv("FOO")) or something equally stupid).

[scatters]

So an attacker able to write to memory would be able to elevate into the ability to... write to memory. That doesn't sound particularly worrisome.

[nocturnial]

In a lot of cases the attacker can only write to a limited range of memory addresses. If that string happens to fall in that range, they can use it to write to other addresses and/or find out where in memory certain things are stored.

So their ability to write to a limited range of addresses can be extended to a larger range.

[a1369209993]

If the attacker can write to string memory, they can overwrite "%s\n\0Hello World" just as easily as "Hello World\n".