How to change embedded tomcat's version in existing spring boot app?

Late to the party I know, was looking for a similar issue, thought I'd share a more literal hint.

You need to override the properties set in spring's parent pom (which is mandatory for this) to suit your case (and compatibility too):

<properties>
......
    <tomcat.version>9.0.5</tomcat.version>
......
<properties>

This is according to [Introduction to Spring][1]. Their example shows many other dependencies cherry-picked. [1]: http://www.springboottutorial.com/spring-boot-starter-parent

If you are using spring boot gradle plugin and spring boot starters ..you can customise the version by setting maven project properties in build.gradle.

ext['tomcat.version'] = '8.5.34'

You can find all the external dependencies that can be customised in spring-boot-dependencies