The Windows installer for Apache Tomcat 6.0.0 through 6.0.20, 5.5.0 through 5.5.28, and possibly earlier versions uses a blank default password for the administrative user, which allows remote attackers to gain privileges.

Apache Tomcat 4.1.0 through 4.1.39, 5.5.0 through 5.5.27, and 6.0.0 through 6.0.18, when the Java AJP connector and mod_jk load balancing are used, allows remote attackers to cause a denial of service (application outage) via a crafted request with invalid headers, related to temporary blocking of connectors that have encountered errors, as demonstrated by an error involving a malformed HTTP Host header.

Apache Tomcat 4.1.0 through 4.1.39, 5.5.0 through 5.5.27, and 6.0.0 through 6.0.18, when FORM authentication is used, allows remote attackers to enumerate valid usernames via requests to /j_security_check with malformed URL encoding of passwords, related to improper error checking in the (1) MemoryRealm, (2) DataSourceRealm, and (3) JDBCRealm authentication realms, as demonstrated by a % (percent) value for the j_password parameter.

The JK Connector (aka mod_jk) 1.2.0 through 1.2.26 in Apache Tomcat allows remote attackers to obtain sensitive information via an arbitrary request from an HTTP client, in opportunistic circumstances involving (1) a request from a different client that included a Content-Length header but no POST data or (2) a rapid series of requests, related to noncompliance with the AJP protocol's requirements for requests containing Content-Length headers.

Cross-site scripting (XSS) vulnerability in jsp/cal/cal2.jsp in the calendar application in the examples web application in Apache Tomcat 4.1.0 through 4.1.39, 5.5.0 through 5.5.27, and 6.0.0 through 6.0.18 allows remote attackers to inject arbitrary web script or HTML via the time parameter, related to "invalid HTML."

Apache Tomcat 5.5.0 and 4.1.0 through 4.1.31 allows remote attackers to bypass an IP address restriction and obtain sensitive information via a request that is processed concurrently with another request but in a different thread, leading to an instance-variable overwrite associated with a "synchronization problem" and lack of thread safety, and related to RemoteFilterValve, RemoteAddrValve, and RemoteHostValve.

Apache Tomcat 4.1.0 through 4.1.37, 5.5.0 through 5.5.26, and 6.0.0 through 6.0.16, when a RequestDispatcher is used, performs path normalization before removing the query string from the URI, which allows remote attackers to conduct directory traversal attacks and read arbitrary files via a .. (dot dot) in a request parameter.

Absolute path traversal vulnerability in Apache Tomcat 4.0.0 through 4.0.6, 4.1.0, 5.0.0, 5.5.0 through 5.5.25, and 6.0.0 through 6.0.14, under certain configurations, allows remote authenticated users to read arbitrary files via a WebDAV write request that specifies an entity with a SYSTEM tag.