The code in Apache Tomcat 9.0.0.M1 to 9.0.0.M11, 8.5.0 to 8.5.6, 8.0.0.RC1 to 8.0.38, 7.0.0 to 7.0.72, and 6.0.0 to 6.0.47 that parsed the HTTP request line permitted invalid characters. This could be exploited, in conjunction with a proxy that also permitted the invalid characters but with a different interpretation, to inject data into the HTTP response. By manipulating the HTTP response the attacker could poison a web-cache, perform an XSS attack and/or obtain sensitive information from requests other then their own.

It was discovered that a programming error in the processing of HTTPS requests in the Apache Tomcat servlet and JSP engine may result in denial of service via an infinite loop. The denial of service is easily achievable as a consequence of backporting a CVE-2016-6816 fix but not backporting the fix for Tomcat bug 57544. Distributions affected by this backporting issue include Debian (before 7.0.56-3+deb8u8 and 8.0.14-1+deb8u7 in jessie) and Ubuntu.