Guava library upgrade (breaking changes!)

Jenkins bundles Guava, a core Java library from Google. Beginning with Jenkins 2.320 (released on November 10, 2021), Jenkins has upgraded the Guava library from 11.0.1 (released on January 9, 2012) to 31.0.1 (released on September 27, 2021). Plugins have already been prepared to support the new version of Guava in JEP-233. Use the Plugin Manager to upgrade all plugins before and after upgrading to Jenkins 2.320.

Many security-conscious organizations using, or planning to use, Jenkins run off-the-shelf security scanners to look for known vulnerabilities. These commonly flag the obsolete Guava library as susceptible to a serialization-related vulnerability (CVE-2018-10237) and recommend upgrading. While Jenkins uses JEP-200 to form an explicit list of allowed classes for deserialization, and the two Guava classes affected by CVE-2018-10237 are not and will never be added to the list, it is time-consuming for the security team to respond to purported security reports and for users to justify exemptions from policy to use Jenkins anyway.

Furthermore, the decade-old version of Guava has long been a maintenance burden for Jenkins developers. In a world where Dependabot offers upgrades to libraries released just hours before, it is unpleasant to be working with dependencies that are many years old.

For more information, see JEP-233.

The vast majority of plugins have already been prepared to support the new version of Guava in JEP-233. Jenkins users need only upgrade plugins to compatible versions as documented in the "Released As" field in Jira. It is critical to use the Plugin Manager to upgrade all plugins before and after upgrading to Jenkins 2.320. Failure to upgrade plugins to compatible versions may result in ClassNotFoundException, NoClassDefFoundError, or other low-level Java errors.

If you find a regression in a plugin, please file a bug report in Jira:

When reporting an issue, include the following information:

If you maintain a Jenkins plugin with an open JEP-233 issue, then please check if there is a pull request awaiting merge or release. If you use an unmaintained Jenkins plugin with an open JEP-233 issue, consider stepping up and adopting the plugin to release a compatible version.

We expect to see a bit of disruption from these changes but hope that in the long run they will save time for core and plugin developers and lead to a more secure and stable tool. Please reach out on the developers' list with any questions or suggestions.