Buffer overflow in php7 (Alpine package)

1) Buffer overflow

EUVDB-ID: #VU22304

Risk: High

CVSSv3.1: 7.5 [CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H/E:F/RL:O/RC:C]

CVE-ID: CVE-2019-11043

CWE-ID: CWE-119 - Memory corruption

Exploit availability: Yes

Description

The vulnerability allows a remote attacker to execute arbitrary code on the target system.

The vulnerability exists due to a boundary error in env_path_info in PHP-FPM when processing untrusted input passed via URL. A remote attacker can send a specially crafted HTTP request to the affected server, trigger memory corruption and execute arbitrary code on the target system.

Successful exploitation of this vulnerability may result in complete compromise of vulnerable system but requires that php-fpm is used with nginx and certain nginx configuration was applied:

1. The nginx location directive forwards requests to PHP-FPM
2. The fastcgi_split_path_info directive is present and includes a regular expression beginning with a ‘^’ symbol and ending with a ‘$’ symbol
3. The fastcgi_param directive is used to assign the PATH_INFO variable
4. There are no checks in place to determine whether or not a file exists (e.g., using try_files or an if statemen

Mitigation

Install update from vendor's website.

Vulnerable software versions

php7 (Alpine package): 7.1.9-r0 - 7.1.32-r0

External links

http://git.alpinelinux.org/aports/commit/?id=89bf7fcf675ffb9138a3afe613cb1f7c918b57ac
http://git.alpinelinux.org/aports/commit/?id=bac59df7da74c2932027eda4e6ae0f0d29a54746
http://git.alpinelinux.org/aports/commit/?id=480a917a663e2ea1d3950f0a5d2e3c7b1789091c
http://git.alpinelinux.org/aports/commit/?id=8fcc88fbc7ad864af0b1b56e0986632e07a8861a
http://git.alpinelinux.org/aports/commit/?id=371e976514cfea6e878f60b34c6364fdd04ceccd
http://git.alpinelinux.org/aports/commit/?id=a2f9f39144b5245d048f7df83936d9c6fcf3c443

Q & A

Can this vulnerability be exploited remotely?

Yes. This vulnerability can be exploited by a remote non-authenticated attacker via the Internet.

Is there known malware, which exploits this vulnerability?

No. We are not aware of malware exploiting this vulnerability. However, a fully functional exploit for this vulnerability is available.