CVE-2021-21603

Name: CVE-2021-21603
Creator: NVD / NIST
Published: 2021-01-13T16:15:13.46+00:00
License: https://creativecommons.org/publicdomain/zero/1.0/

MEDIUMCVSS 5.4/10EPSS 1.03%

Last modified Jun 17, 2026

CVE-2021-21603 is a medium-severity vulnerability rated 5.4/10 on the CVSS scale. 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.. EPSS estimates a 1.03% chance of exploitation in the next 30 days.

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.

Metrics

CVSS 3.1

5.4/10

CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:L/I:L/A:N

EPSS Probability

1.03%

59.3th percentile

Probability of exploitation in the next 30 days. Learn more

Weakness Enumeration

CWE-79

Affected Software

Vendor	Product	Versions
Jenkins	Jenkins	<= 2.263.1
Jenkins	Jenkins	<= 2.274

References

https://www.jenkins.io/security/advisory/2021-01-13/#SECURITY-1889Vendor Advisory
https://www.jenkins.io/security/advisory/2021-01-13/#SECURITY-1889Vendor Advisory

Timeline

Published: Jan 13, 2021
Last Modified: Jun 17, 2026
Status: Modified

Frequently Asked Questions

What is CVE-2021-21603?

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.

How severe is CVE-2021-21603?

CVE-2021-21603 has a CVSS score of 5.4/10 (MEDIUM severity). The EPSS model estimates a 1.03% probability of exploitation in the next 30 days.

How do I fix CVE-2021-21603?

Check the vendor references and advisories linked above for patched versions and mitigation guidance. You can also run a Strix scan to test if your systems are affected.

Are you affected by CVE-2021-21603?

Run a free Strix scan to check your systems for this vulnerability.

Scan your code now

Source: NVD / NIST