Code Execution Flaws Patched in Apache Tomcat

Several vulnerabilities, including ones that allow remote attackers to execute arbitrary code, have been patched in recent weeks in Apache Tomcat.

Developed by The Apache Software Foundation, Apache Tomcat is an open source implementation of the Java Servlet, JavaServer Pages (JSP), Java WebSocket and Java Expression Language technologies. Tomcat is said to be the most widely used web application server, with a presence in more than 70% of enterprise data centers.

Apache Tomcat developers informed users on Tuesday that the product is affected by a remote code execution vulnerability.

The flaw, tracked as CVE-2017-12617 and classified as “important” severity, has been addressed with the release of versions 9.0.1, 8.5.23, 8.0.47 and 7.0.82. All previous 9.x, 8.5.x, 8.0.x and 7.0.x versions are impacted.

The vulnerability affects systems that have the HTTP PUT method enabled and it allows attackers to upload a malicious JSP file to a targeted server using a specially crafted request. The server would then execute the code in the JSP file when the file was requested. A proof-of-concept (PoC) exploit is publicly available.

While this sounds like a serious vulnerability, in only affects systems that have the default servlet configured with the readonly parameter set to false or the WebDAV servlet enabled with the readonly  parameter set to false.

“Since this feature is typically not wanted, most publicly exposed system won’t have readonly set to false and are thus not affected,” explained Peter Stöckli of Alphabot Security.

This vulnerability is very similar to CVE-2017-12615, which Apache Tomcat developers patched on September 19 with the release of version 7.0.81. CVE-2017-12617 has been described by one individual as a “bypass for CVE-2017-12615.”

The Apache Tomcat 7 update released in September also patched CVE-2017-12616, a flaw that allows an attacker to bypass security constraints and view the source code of JSPs via a specially crafted request.

Apache Tomcat vulnerabilities are less likely to be exploited in the wild, compared to Apache Struts 2 flaws, which have been used in many attacks, including to breach the systems of U.S. credit reporting agency Equifax.

There was a worm targeting Apache Tomcat servers a few years ago, but it did not leverage any vulnerabilities; it used common username and password combinations to gain access.