How severe is CVE-2021-21660?

CVE-2021-21660 has a CVSS 3.x base score of 5.4, rated medium severity. It is exploitable over network with low attack complexity, requires low privileges and user interaction. Impact on confidentiality is low, integrity low, and availability none.

Is CVE-2021-21660 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (61st percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2021-21660?

CVE-2021-21660 affects Jenkins Markdown Formatter. See the affected-products list for the exact vulnerable versions.

How do I fix CVE-2021-21660?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.

When was CVE-2021-21660 published?

CVE-2021-21660 was published on 2021-05-25 and last updated on 2026-06-17.

CVE-2021-21660

CVE-2021-21660 is a medium-severity vulnerability in Jenkins Markdown Formatter with a CVSS 3.x base score of 5.4. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-79.

Key facts

Severity: Medium (CVSS 3.x base score 5.4)
CVSS v2: 3.5
EPSS exploit prediction: 1% (61st percentile)
Actively exploited: Not listed in CISA KEV
Weakness: CWE-79
Affected product: Jenkins Markdown Formatter
Published: 2021-05-25
Last modified: 2026-06-17

Description

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.

Frequently asked questions

What is CVE-2021-21660?: 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.
How severe is CVE-2021-21660?: CVE-2021-21660 has a CVSS 3.x base score of 5.4, rated medium severity. It is exploitable over network with low attack complexity, requires low privileges and user interaction. Impact on confidentiality is low, integrity low, and availability none.
Is CVE-2021-21660 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (61st percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2021-21660?: CVE-2021-21660 affects Jenkins Markdown Formatter. See the affected-products list for the exact vulnerable versions.
How do I fix CVE-2021-21660?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.
When was CVE-2021-21660 published?: CVE-2021-21660 was published on 2021-05-25 and last updated on 2026-06-17.

References

Affected products (1)

cpe:2.3:a:jenkins:markdown_formatter:*:*:*:*:*:jenkins:*:*

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