(RHSA-2016:1422) Important: httpd security and bug fix update

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

Security Fix(es):

• It was discovered that httpd used the value of the Proxy header from HTTP requests to initialize the HTTP_PROXY environment variable for CGI scripts, which in turn was incorrectly used by certain HTTP client implementations to configure the proxy for outgoing HTTP requests. A remote attacker could possibly use this flaw to redirect HTTP requests performed by a CGI script to an attacker-controlled proxy via a malicious HTTP request. (CVE-2016-5387)

Note: After this update, httpd will no longer pass the value of the Proxy request header to scripts via the HTTP_PROXY environment variable.

Red Hat would like to thank Scott Geary (VendHQ) for reporting this issue.

Bug Fix(es):

• In a caching proxy configuration, the mod_cache module would treat content as stale if the Expires header changed when refreshing a cached response. As a consequence, an origin server returning content without a fixed Expires header would not be treated as cacheable. The mod_cache module has been fixed to ignore changes in the Expires header when refreshing content. As a result, such content is now cacheable, improving performance and reducing load at the origin server. (BZ#1347648)

• The HTTP status code 451 “Unavailable For Legal Reasons” was not usable in the httpd configuration. As a consequence, modules such as mod_rewrite could not be configured to return a 451 error if required for legal purposes. The 451 status code has been added to the list of available error codes, and modules can now be configured to return a 451 error if required. (BZ#1353269)