Multiple vulnerabilities in Apache HTTP Server

Published: 2016-12-21 | Updated: 2017-06-08

Risk	Medium
Patch available	YES
Number of vulnerabilities	4
CVE-ID	CVE-2016-8743 CVE-2016-2161 CVE-2016-0736 CVE-2016-5387
CWE-ID	CWE-20 CWE-696 CWE-284
Exploitation vector	Network
Public exploit	Public exploit code for vulnerability #3 is available. Public exploit code for vulnerability #4 is available.
Vulnerable software	Apache HTTP Server Server applications / Web servers
Vendor	Apache Foundation

Security Bulletin

This security bulletin contains information about 4 vulnerabilities.

A remote attacker can perform perform spoofing attacks, cause denial of service and potentially compromise vulnerable system.

1) Spoofing attack

EUVDB-ID: #VU1961

Risk: Medium

CVSSv4.0: 2.7 [CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:L/VI:L/VA:N/SC:N/SI:N/SA:N/E:U/U:Green]

CVE-ID: CVE-2016-8743

CWE-ID: CWE-20 - Improper input validation

Exploit availability: No

Description

The vulnerability allows a remote attacker to perform spoofing attack.

The vulnerability exists due to insufficient sanitization of HTTP request, which contain whitespace characters. A remote attacker can send a specially crafted HTTP request, containing CR, FF, VTAB characters followed by CRLF sequence and inject arbitrary data in server response.

Successful exploitation of this vulnerability may result in content spoofing, web cache poisoning and XSS attacks.

Mitigation

Install the latest version Apache HTTP Server 2.4.25 or 2.2.32.

Vulnerable software versions

Apache HTTP Server: 2.2.0 - 2.4.23

CPE2.3

External links

https://httpd.apache.org/security/vulnerabilities_24.html
https://www.apache.org/dist/httpd/CHANGES_2.2.32

Q & A

Can this vulnerability be exploited remotely?

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

How the attacker can exploit this vulnerability?

The attacker would have to send a specially crafted request to the affected application in order to exploit this vulnerability.

Is there known malware, which exploits this vulnerability?

No. We are not aware of malware exploiting this vulnerability.

2) Improper input validation

EUVDB-ID: #VU1886

Risk: Medium

CVSSv4.0: 6.6 [CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N/E:U/U:Green]

CVE-ID: CVE-2016-2161

CWE-ID: CWE-20 - Improper input validation

Exploit availability: No

Description

The vulnerability allows a remote attacker to cause denial of service attack.

The vulnerability exists due to input validation error in mod_auth_digest module when parsing malicious HTTP requests. A remote attacker can send a specially crafted HTTP request to affected server and cause server crash.

Successful exploitation of the vulnerability will result in crash of each server instance.

Mitigation

Install the latest version Apache HTTP Server 2.4.25.

Vulnerable software versions

Apache HTTP Server: 2.2.0 - 2.4.23

CPE2.3

External links

https://httpd.apache.org/security/vulnerabilities_24.html

Q & A

Can this vulnerability be exploited remotely?

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

How the attacker can exploit this vulnerability?

The attacker would have to send a specially crafted request to the affected application in order to exploit this vulnerability.

Is there known malware, which exploits this vulnerability?

No. We are not aware of malware exploiting this vulnerability.

3) Padding oracle attack

EUVDB-ID: #VU1800

Risk: Low

CVSSv4.0: 2.1 [CVSS:4.0/AV:A/AC:L/AT:N/PR:N/UI:N/VC:L/VI:L/VA:N/SC:N/SI:N/SA:N/E:P/U:Clear]

CVE-ID: CVE-2016-0736

CWE-ID: CWE-696 - Incorrect Behavior Order

Exploit availability: Yes

Description

The vulnerability allows a remote attacker to obtain potentially sensitive information.

The vulnerability exists due to an error in Apache mod_session_crypto implementation. A remote attacker with ability to intercept traffic can decipher potentially sensitive information or tamper with data.

Successful exploitation may allow an attacker to perform padding oracle attack against vulnerable web server and obtain potentially sensitive information.

Mitigation

The vulnerability is fixed in Apache HTTP Server 2.4.25.

Vulnerable software versions

Apache HTTP Server: 2.4.1 - 2.4.23

CPE2.3

External links

https://httpd.apache.org/security/vulnerabilities_24.html

Q & A

Can this vulnerability be exploited remotely?

Yes. This vulnerability can be exploited by a remote non-authenticated attacker via the local network (LAN).

How the attacker can exploit this vulnerability?

The attacker would have to send a specially crafted request to the affected application in order to exploit this vulnerability.

Is there known malware, which exploits this vulnerability?

No. We are not aware of malware exploiting this vulnerability. However, proof of concept for this vulnerability is available.

4) Httpoxy issue

EUVDB-ID: #VU337

Risk: Medium

CVSSv4.0: 8.2 [CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N/E:P/U:Green]

CVE-ID: CVE-2016-5387

CWE-ID: CWE-284 - Improper Access Control

Exploit availability: No

Description

The vulnerability allows a remote attacker to obtain potentially sensitive information and compromise vulnerable server.

The vulnerability exists due to a design error in multiple implementations of web servers. A remote unauthenticated attacker can use a specially crafted Proxy header in HTTP request to influence HTTP_PROXY environment variable and redirect application’s HTTP traffic to arbitrary proxy server.

Successful exploitation of this vulnerability may allow an attacker to gain unauthorized access to sensitive information and compromise vulnerable server.

This vulnerability is known as httppoxy.

Mitigation

Install the latest version 2.4.25 or 2.2.32 from vendor's website.

Vulnerable software versions

Apache HTTP Server: 2.2.0 - 2.4.23

CPE2.3

External links

https://httpd.apache.org/security/vulnerabilities_24.html
https://www.apache.org/dist/httpd/CHANGES_2.2.32

Q & A

Can this vulnerability be exploited remotely?

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

How the attacker can exploit this vulnerability?

The attacker would have to send a specially crafted request to the affected application in order to exploit this vulnerability.

Is there known malware, which exploits this vulnerability?

No. We are not aware of malware exploiting this vulnerability. However, proof of concept for this vulnerability is available.