CVE-2021-21603 XSS vulnerability in Jenkins notification bar

What is CVE-2021-21603?

CVE-2021-21603 is a medium-severity cross-site scripting vulnerability in Jenkins Jenkins, published on 13 Jan 2021. Any signed-in user can exploit it over the network, and only if a user opens a file or follows a link.

Official description

Jenkins 2.274 and earlier, LTS 2.263.1 and earlier does not escape notification bar response contents, resulting in a cross-site scripting (XSS) vulnerability.

Weakness: CWE-79

Which versions are affected by CVE-2021-21603?

5 open source packages ship an affected version, including org.jenkins-ci.main:jenkins-core and jenkins. It affects 1 product.

Products include Jenkins Jenkins.

How do I fix CVE-2021-21603?

Upgrade org.jenkins-ci.main:jenkins-core to 2.275 or later.

Escape output for the context it lands in and set a strict Content Security Policy. Upgrading the affected component is the real fix. More about Cross-site scripting.

Is CVE-2021-21603 being exploited?

There is no known exploitation of CVE-2021-21603 in the wild and no public exploit code.

Other vulnerabilities in Jenkins Jenkins

• CVE-2024-23897 Jenkins Command Line Interface (CLI) Path Traversal Exploited Critical 9.8
• CVE-2018-1000861 Jenkins Stapler Web Framework Deserialization of Untrusted Data Exploited Critical 9.8
• CVE-2017-1000353 Jenkins Remote Code Execution Exploited Critical 9.8
• CVE-2015-5317 Jenkins User Interface (UI) Information Disclosure Exploited High 7.5
• CVE-2021-21690 Multiple vulnerabilities allow bypassing path filtering of agent-to-controller access control in Jenkins Critical 9.8

All Jenkins Jenkins vulnerabilities

Sources

• CVE record
• NVD
• OSV
• GitHub advisory
• How this page is made

Also known as BIT-jenkins-2021-21603, GHSA-98gq-6hxg-52r6.