In plain words
Imagine you are sending a package to someone, but you put the wrong address on it, so it gets lost or causes trouble. This bug is like putting a wrong address on a package that the Apache server is trying to send, which can cause the server to crash.
What's broken
The bug is in the mod_proxy_html part of the Apache HTTP Server¹, which is a module that helps format HTML content. The bug is called an out-of-bounds Write vulnerability², which means that an attacker could send a specially crafted HTTP response body³ that would cause the server to write data outside of where it is supposed to, leading to a crash. The affected versions are Apache HTTP Server 2.4.0 through 2.4.68.
How it actually works
Here's how it works: when the Apache server receives an HTTP response body, it uses the mod_proxy_html module to format the HTML content. If an attacker sends a crafted HTTP response body, it can cause the server to write data outside of the allowed area, which can lead to a crash. This is because the server is not properly checking the boundaries of where it can write data.
Proof of concept
There is a public reference to this vulnerability, but it is not clear from the source if there is a proof-of-concept (PoC)⁴ that demonstrates the bug. A PoC would show that the flaw is real and can be reached by an attacker, not just theoretical.
Is it real
It is not clear from the source if this bug is being actively exploited in the wild. The severity is listed as low, which means it's not very critical.
What to do
To fix this bug, you would need to update your Apache HTTP Server to a version that is not affected by this vulnerability.
Terms
- ¹ Apache HTTP Server
- , a software module that helps format HTML content
- ² out-of-bounds Write vulnerability
- , a type of vulnerability that allows an attacker to write data outside of where it is supposed to
- ³ HTTP response body
- , the content of an HTTP response
- ⁴ proof-of-concept
- , a demonstration that a vulnerability is real and can be reached by an attacker