CVE-2020-1938Apache Tomcat Improper Privilege Management Vulnerability

What it is

The record does not classify the weakness yet; the description below says what the reporter found.

How it is reached

An attacker can exploit it over the network, without an account, and nobody has to click anything.

What an attacker gains

A successful attack can read the data it protects, change data or behaviour and take it offline.

Is it being exploited?

CISA added it to the Known Exploited Vulnerabilities catalog on 2022-03-03: it is being exploited in the wild. It can be exploited automatically, at scale. EPSS estimates a 99% chance of exploitation activity in the next 30 days, higher than 100% of scored CVEs.

What to do

1. Treat it as urgent: it is on CISA's KEV list. CISA's deadline for US federal agencies: 2022-03-17.
2. Upgrade Apache Tomcat to a fixed version for your release line (7.0.100, 8.5.51, 9.0.31). The patch notes are linked below.
3. Until it is patched, keep it off the internet or behind a VPN, allowlist or authenticating proxy.
4. Check exposed instances for signs of compromise, not only for the version.

Description from NVD

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.