SB2019040407 - Ubuntu update for Apache HTTP Server

Security Bulletin ID SB2019040407

Severity

Medium

Patch available

YES

Number of vulnerabilities 6

Exploitation vector Remote access

Highest impact Denial of service

Breakdown by Severity

Low
Medium
High
Critical

Description

This security bulletin contains information about 6 secuirty vulnerabilities.

1) Privilege escalation (CVE-ID: CVE-2019-0211)

The vulnerability allows a local user to escalate privileges on the system.

The vulnerability exists within MPM implementation due to the application does not properly maintain each child's listener bucket number in the scoreboard that may lead to unprivileged code or scripts run by server (e.g. via mod_php) to modify the scoreboard and abuse the privileged main process.

A local user can execute arbitrary code on the system with privileges of the Apache HTTP Server code process.

2) Input validation error (CVE-ID: CVE-2018-17189)

The vulnerability allows a remote attacker to cause DoS condition on the target system.

The weakness exists due to an error when handling malicious input. A remote attacker can send a specially crafted request bodies in a slow loris way to plain resources and cause the h2 stream for that request unnecessarily occupied a server thread cleaning up that incoming data.

3) Security restrictions bypass (CVE-ID: CVE-2018-17199)

The vulnerability allows a remote attacker to bypass security restrictions on the target system.

The weakness exists due to mod_session checks the session expiry time before decoding the session. A remote attacker сan cause session expiry time to be ignored for mod_session_cookie sessions since the expiry time is loaded when the session is decoded and reuse old session credentials or session IDs, which the attacker could use to access web pages previously accessed by a targeted user.

4) Use-after-free (CVE-ID: CVE-2019-0196)

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

The vulnerability exists due to a use-after-free error within the mod_http2 module when processing HTTP/2 requests. A remote attacker can make the application to access freed memory during string comparison when determining the method of a request and process the request incorrectly.

Successful exploitation of the vulnerability may allow an attacker to gain access to sensitive information or perform a denial of service attack.

5) Race condition (CVE-ID: CVE-2019-0217)

The vulnerability allows a remote authenticated user to impersonate other users.

The vulnerability exists due to a race condition within the mod_auth_digests module. A remote authenticated attacker can send a series of requests and impersonate other users under a threaded MPM.

6) Input validation error (CVE-ID: CVE-2019-0220)

The vulnerability allows a remote attacker to bypass certain security restrictions.

The vulnerability exists due to the web server does not merge consecutive slashes in URLs, that can lead to incorrect processing of requests when accessing CGI programs. Such web server behavior may lead to security restrictions bypass.

Remediation

Install update from vendor's website.

References

https://usn.ubuntu.com/3937-1/