Synopsis

Moderate: httpd24-httpd security, bug fix, and enhancement update

Type/Severity

Security Advisory: Moderate

Topic

Updated httpd24 packages are now available as a part of Red Hat Software Collections 2.4 for Red Hat Enterprise Linux.

Red Hat Product Security has rated this update as having a security impact of Moderate. A Common Vulnerability Scoring System (CVSS) base score, which gives a detailed severity rating, is available for each vulnerability from the CVE link(s) in the References section.

Description

The Apache HTTP Server is a powerful, efficient, and extensible web server. The httpd24 packages provide a recent stable release of version 2.4 of the Apache HTTP Server, along with the mod_auth_kerb module.

The httpd24 Software Collection has been upgraded to version 2.4.25, which provides a number of bug fixes and enhancements over the previous version. For detailed changes, see the Red Hat Software Collections 2.4 Release Notes linked from the References section. (BZ#1404778)

Security Fix(es):

• It was discovered that the mod_session_crypto module of httpd did not use any mechanisms to verify integrity of the encrypted session data stored in the user's browser. A remote attacker could use this flaw to decrypt and modify session data using a padding oracle attack. (CVE-2016-0736)
• A denial of service flaw was found in httpd's mod_http2 module. A remote attacker could use this flaw to block server threads for long times, causing starvation of worker threads, by manipulating the flow control windows on streams. (CVE-2016-1546)
• It was discovered that the mod_auth_digest module of httpd did not properly check for memory allocation failures. A remote attacker could use this flaw to cause httpd child processes to repeatedly crash if the server used HTTP digest authentication. (CVE-2016-2161)
• It was discovered that the HTTP parser in httpd incorrectly allowed certain characters not permitted by the HTTP protocol specification to appear unencoded in HTTP request headers. If httpd was used in conjunction with a proxy or backend server that interpreted those characters differently, a remote attacker could possibly use this flaw to inject data into HTTP responses, resulting in proxy cache poisoning. (CVE-2016-8743)

Note: The fix for the CVE-2016-8743 issue causes httpd to return "400 Bad Request" error to HTTP clients which do not strictly follow HTTP protocol specification. A newly introduced configuration directive "HttpProtocolOptions Unsafe" can be used to re-enable the old less strict parsing. However, such setting also re-introduces the CVE-2016-8743 issue.

• A vulnerability was found in httpd's handling of the LimitRequestFields directive in mod_http2, affecting servers with HTTP/2 enabled. An attacker could send crafted requests with headers larger than the server's available memory, causing httpd to crash. (CVE-2016-8740)

Solution

For details on how to apply this update, which includes the changes described in this advisory, refer to:

https://access.redhat.com/articles/11258

After installing the updated packages, the httpd daemon will be restarted automatically.

Affected Products

• Red Hat Software Collections (for RHEL Server) 1 for RHEL 7.7 x86_64
• Red Hat Software Collections (for RHEL Server) 1 for RHEL 7.6 x86_64
• Red Hat Software Collections (for RHEL Server) 1 for RHEL 7.5 x86_64
• Red Hat Software Collections (for RHEL Server) 1 for RHEL 7.4 x86_64
• Red Hat Software Collections (for RHEL Server) 1 for RHEL 7.3 x86_64
• Red Hat Software Collections (for RHEL Server) 1 for RHEL 7 x86_64
• Red Hat Software Collections (for RHEL Server) 1 for RHEL 6.7 x86_64
• Red Hat Software Collections (for RHEL Server) 1 for RHEL 6 x86_64
• Red Hat Software Collections (for RHEL Workstation) 1 for RHEL 7 x86_64
• Red Hat Software Collections (for RHEL Workstation) 1 for RHEL 6 x86_64

Fixes

• BZ - 1329639 - error in service httpd24-httpd configtest
• BZ - 1335616 - Backport Apache PR58118 to fix mod_proxy_fcgi spamming non-errors: AH01075: Error dispatching request to : (passing brigade to output filters)
• BZ - 1336350 - CVE-2016-1546 httpd: mod_http2 denial-of-service by thread starvation
• BZ - 1401528 - CVE-2016-8740 httpd: Incomplete handling of LimitRequestFields directive in mod_http2
• BZ - 1406744 - CVE-2016-0736 httpd: Padding Oracle in Apache mod_session_crypto
• BZ - 1406753 - CVE-2016-2161 httpd: DoS vulnerability in mod_auth_digest
• BZ - 1406822 - CVE-2016-8743 httpd: Apache HTTP Request Parsing Whitespace Defects
• BZ - 1414037 - mod_proxy_fcgi regression in 2.4.23+
• BZ - 1432249 - must fail startup with conflicting Listen directives
• BZ - 1433474 - wrong requires of httpd24-httpd and httpd24-httpd-tools

CVEs

• CVE-2016-0736
• CVE-2016-1546
• CVE-2016-2161
• CVE-2016-8740
• CVE-2016-8743
• CVE-2020-11985

References