CVE-2020-1938

When using the Apache JServ Protocol (AJP), care must be taken when trusting incoming connections to Apache Tomcat. Tomcat treats AJP connections as having higher trust than, for example, a similar HTTP connection. If such connections are available to an attacker, they can be exploited in ways that may be surprising. In Apache Tomcat 9.0.0.M1 to 9.0.0.30, 8.5.0 to 8.5.50 and 7.0.0 to 7.0.99, Tomcat shipped with an AJP Connector enabled by default that listened on all configured IP addresses. It was expected (and recommended in the security guide) that this Connector would be disabled if not required. This vulnerability report identified a mechanism that allowed: returning arbitrary files from anywhere in the web application, processing any file in the web application as a JSP Further, if the web application allowed file upload and stored those files within the web application (or the attacker was able to control the content of the web application by some other means) then this, along with the ability to process a file as a JSP, made remote code execution possible. It is important to note that mitigation is only required if an AJP port is accessible to untrusted users. Users wishing to take a defence-in-depth approach and block the vector that permits returning arbitrary files and execution as JSP may upgrade to Apache Tomcat 9.0.31, 8.5.51 or 7.0.100 or later. A number of changes were made to the default AJP Connector configuration in 9.0.31 to harden the default configuration. It is likely that users upgrading to 9.0.31, 8.5.51 or 7.0.100 or later will need to make small changes to their configurations.

The application assigns, modifies, tracks, or checks privileges incorrectly, allowing a user to gain elevated access. Typical impact: privilege escalation beyond the intended level.

CVE-2020-1938 has a CVSS score of 9.8 (Critical). The vector is network-reachable, no privileges required, and no user interaction. A CVSS score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether this affects your application depends on whether the vulnerable code is present and reachable in your environment. A fixed version is available (9.0.31, 8.5.51, 7.0.100); upgrading removes the vulnerable code path.

Kodem intelligence

1. What is CVE-2020-1938? CVE-2020-1938 is a critical-severity improper privilege management vulnerability in org.apache.tomcat.embed:tomcat-embed-core (maven), affecting versions >= 9.0.0, < 9.0.31. It is fixed in 9.0.31, 8.5.51, 7.0.100. The application assigns, modifies, tracks, or checks privileges incorrectly, allowing a user to gain elevated access.
2. How severe is CVE-2020-1938? CVE-2020-1938 has a CVSS score of 9.8 (Critical). This score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether it represents real risk in your environment depends on whether the vulnerable code is present and reachable.
3. Which versions of org.apache.tomcat.embed:tomcat-embed-core are affected by CVE-2020-1938? org.apache.tomcat.embed:tomcat-embed-core (maven) versions >= 9.0.0, < 9.0.31 is affected.
4. Is there a fix for CVE-2020-1938? Yes. CVE-2020-1938 is fixed in 9.0.31, 8.5.51, 7.0.100. Upgrade to this version or later.
5. Is CVE-2020-1938 exploitable, and should I be worried? Whether CVE-2020-1938 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
6. What actually determines whether CVE-2020-1938 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
7. How do I fix CVE-2020-1938?
   • Upgrade org.apache.tomcat.embed:tomcat-embed-core to 9.0.31 or later
   • Upgrade org.apache.tomcat.embed:tomcat-embed-core to 8.5.51 or later
   • Upgrade org.apache.tomcat.embed:tomcat-embed-core to 7.0.100 or later