CVE-2021-21660

XSS vulnerability in Jenkins Markdown Formatter Plugin

5.4 MediumFix available

Jenkins Markdown Formatter Plugin 0.1.0 and earlier does not sanitize crafted link target URLs, resulting in a stored cross-site scripting (XSS) vulnerability exploitable by attackers with the ability to edit any description rendered using the configured markup formatter.

Attack profile

How easy it is to exploit

Attack vector: Network
Complexity: Low
Privileges needed: Low
User interaction: Required

What an attacker can affect

Confidentiality: Low
Integrity: Low
Availability: None

Exploit likelihood

1.09%Up 0.3 points since May 26, 2021

What each source reports

NVD Score used 5.4

Record: CVE-2021-21660
CVSS 3.1: 5.4 MediumCVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:L/I:L/A:N
CVSS 2.0: 3.5 LowAV:N/AC:M/Au:S/C:N/I:P/A:N
Weakness: CWE-79
Updated: 2026-11-02

CVE List No score

Record: CVE-2021-21660
Updated: 2026-11-02

EUVDEUVD-2022-5842 No score

Record: EUVD-2022-5842
Updated: 2026-11-03

GitHub AdvisoriesGHSA-xqpp-26pp-2365 5.4

XSS vulnerability in Jenkins Markdown Formatter Plugin

Jenkins Markdown Formatter Plugin 0.1.0 and earlier uses a Markdown library to parse Markdown that does not escape crafted link target URLs.

This results in a stored cross-site scripting (XSS) vulnerability exploitable by attackers with the ability to edit any description rendered using the configured markup formatter.

Jenkins Markdown Formatter Plugin 0.2.0 uses a different Markdown library that is not affected by this problem.

Record: GHSA-xqpp-26pp-2365
CVSS 3.1: 5.4 MediumCVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:L/I:L/A:N
Weakness: CWE-79
Updated: 2026-11-02

OSVGHSA-xqpp-26pp-2365 5.4

XSS vulnerability in Jenkins Markdown Formatter Plugin

Jenkins Markdown Formatter Plugin 0.1.0 and earlier uses a Markdown library to parse Markdown that does not escape crafted link target URLs.

This results in a stored cross-site scripting (XSS) vulnerability exploitable by attackers with the ability to edit any description rendered using the configured markup formatter.

Jenkins Markdown Formatter Plugin 0.2.0 uses a different Markdown library that is not affected by this problem.

Record: GHSA-xqpp-26pp-2365
CVSS 3.1: 5.4 MediumCVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:L/I:L/A:N
Weakness: CWE-79
Updated: 2026-11-02

Affected products

Affected packages

Affected packages
Package	Affected	Fixed
`io.jenkins.plugins:markdown-formatter` Maven	through 0.1.0	0.2.0
`io.jenkins.plugins:markdown-formatter` Maven	before 0.2.0, plus listed versions 0.1.0	0.2.0

History

History
Recorded	Changed	Sources
Nov 3, 2026	aliases	EUVD
Nov 2, 2026	first indexed	CVE List, GitHub Advisories, NVD, OSV

Dates are when Every CVE recorded each change. Upstream dates may differ.

In short

CVE-2021-21660 is a medium vulnerability (CVSS 5.4) in Jenkins Markdown Formatter, published May 25, 2021. No source lists public exploit code. EPSS puts the chance of exploitation in the next 30 days at 1.09%, the 65th percentile. Fixed in io.jenkins.plugins:markdown-formatter 0.2.0.