RHSA-2017:1161: Moderate: httpd24-httpd security, bug fix, and enhancement update

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 modauthkerb 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 modsessioncrypto 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 modhttp2 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 modauthdigest 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 modhttp2, 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)