Moderate: httpd security and bug fix update

Synopsis

Moderate: httpd security and bug fix update

Type/Severity

Security Advisory: Moderate

Topic

An update for httpd is now available for Red Hat Enterprise Linux 7.

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 httpd packages provide the Apache HTTP Server, a powerful, efficient, and extensible web server.

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)
  
• 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.

Bug Fix(es):

• When waking up child processes during a graceful restart, the httpd parent process could attempt to open more connections than necessary if a large number of child processes had been active prior to the restart. Consequently, a graceful restart could take a long time to complete. With this update, httpd has been fixed to limit the number of connections opened during a graceful restart to the number of active children, and the described problem no longer occurs. (BZ#1420002)
  
• Previously, httpd running in a container returned the 500 HTTP status code (Internal Server Error) when a connection to a WebSocket server was closed. As a consequence, the httpd server failed to deliver the correct HTTP status and data to a client. With this update, httpd correctly handles all proxied requests to the WebSocket server, and the described problem no longer occurs. (BZ#1429947)
  
• In a configuration using LDAP authentication with the mod_authnz_ldap module, the name set using the AuthLDAPBindDN directive was not correctly used to bind to the LDAP server for all queries. Consequently, authorization attempts failed. The LDAP modules have been fixed to ensure the configured name is correctly bound for LDAP queries, and authorization using LDAP no longer fails. (BZ#1420047)

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 Enterprise Linux Server 7 x86_64
• Red Hat Enterprise Linux Server - Extended Update Support 7.6 x86_64
• Red Hat Enterprise Linux Server - Extended Update Support 7.5 x86_64
• Red Hat Enterprise Linux Server - Extended Update Support 7.4 x86_64
• Red Hat Enterprise Linux Server - Extended Update Support 7.3 x86_64
• Red Hat Enterprise Linux for IBM z Systems 7 s390x
• Red Hat Enterprise Linux for IBM z Systems - Extended Update Support 7.6 s390x
• Red Hat Enterprise Linux for Power, big endian - Extended Update Support 7.6 ppc64
• Red Hat Enterprise Linux for Power, big endian - Extended Update Support 7.5 ppc64
• Red Hat Enterprise Linux for Power, big endian - Extended Update Support 7.3 ppc64
• Red Hat Enterprise Linux EUS Compute Node 7.6 x86_64
• Red Hat Enterprise Linux EUS Compute Node 7.5 x86_64
• Red Hat Enterprise Linux EUS Compute Node 7.4 x86_64
• Red Hat Enterprise Linux Server - AUS 7.6 x86_64
• Red Hat Enterprise Linux Server - AUS 7.4 x86_64
• Red Hat Enterprise Linux Server - AUS 7.3 x86_64
• Red Hat Enterprise Linux Workstation 7 x86_64
• Red Hat Enterprise Linux Desktop 7 x86_64
• Red Hat Enterprise Linux for IBM z Systems - Extended Update Support 7.5 s390x
• Red Hat Enterprise Linux for IBM z Systems - Extended Update Support 7.4 s390x
• Red Hat Enterprise Linux for IBM z Systems - Extended Update Support 7.3 s390x
• Red Hat Enterprise Linux for Power, big endian 7 ppc64
• Red Hat Enterprise Linux for Power, big endian - Extended Update Support 7.4 ppc64
• Red Hat Enterprise Linux for Scientific Computing 7 x86_64
• Red Hat Enterprise Linux EUS Compute Node 7.3 x86_64
• Red Hat Enterprise Linux for Power, little endian 7 ppc64le
• Red Hat Enterprise Linux for Power, little endian - Extended Update Support 7.6 ppc64le
• Red Hat Enterprise Linux for Power, little endian - Extended Update Support 7.5 ppc64le
• Red Hat Enterprise Linux for Power, little endian - Extended Update Support 7.4 ppc64le
• Red Hat Enterprise Linux for Power, little endian - Extended Update Support 7.3 ppc64le
• Red Hat Enterprise Linux Server - TUS 7.6 x86_64
• Red Hat Enterprise Linux Server - TUS 7.3 x86_64
• Red Hat Enterprise Linux Server (for IBM Power LE) - Update Services for SAP Solutions 7.6 ppc64le
• Red Hat Enterprise Linux Server (for IBM Power LE) - Update Services for SAP Solutions 7.4 ppc64le
• Red Hat Enterprise Linux Server (for IBM Power LE) - Update Services for SAP Solutions 7.3 ppc64le
• Red Hat Enterprise Linux Server - Update Services for SAP Solutions 7.6 x86_64
• Red Hat Enterprise Linux Server - Update Services for SAP Solutions 7.4 x86_64
• Red Hat Enterprise Linux Server - Update Services for SAP Solutions 7.3 x86_64

Fixes

• 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 - 1420002 - Backport fix for issue with graceful restart taking very long time sometimes
• BZ - 1420047 - AuthLDAPBindDN might not be used for some LDAP searches causing LDAP authz failures
• BZ - 1429947 - Backport: mod_proxy_wstunnel - AH02447: err/hup on backconn

CVEs

• CVE-2016-0736
• CVE-2016-2161
• CVE-2016-8743

References

• https://access.redhat.com/security/updates/classification/#moderate