How severe is CVE-2021-23980?

CVE-2021-23980 has a CVSS 3.x base score of 6.1, rated medium severity. It is exploitable over network with low attack complexity, requires no privileges and user interaction. Impact on confidentiality is low, integrity low, and availability none.

Is CVE-2021-23980 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (38th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2021-23980?

CVE-2021-23980 affects Mozilla Bleach. See the affected-products list for the exact vulnerable versions.

How do I fix CVE-2021-23980?

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

When was CVE-2021-23980 published?

CVE-2021-23980 was published on 2023-02-16 and last updated on 2026-06-17.

CVE-2021-23980

CVE-2021-23980 is a medium-severity vulnerability in Mozilla Bleach with a CVSS 3.x base score of 6.1. 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 6.1)
EPSS exploit prediction: 0% (38th percentile)
Actively exploited: Not listed in CISA KEV
Weakness: CWE-79
Affected product: Mozilla Bleach
Published: 2023-02-16
Last modified: 2026-06-17

Description

A mutation XSS affects users calling bleach.clean with all of: svg or math in the allowed tags p or br in allowed tags style, title, noscript, script, textarea, noframes, iframe, or xmp in allowed tags the keyword argument strip_comments=False Note: none of the above tags are in the default allowed tags and strip_comments defaults to True.

Frequently asked questions

What is CVE-2021-23980?: A mutation XSS affects users calling bleach.clean with all of: svg or math in the allowed tags p or br in allowed tags style, title, noscript, script, textarea, noframes, iframe, or xmp in allowed tags the keyword argument strip_comments=False Note: none of the above tags are in the default allowed tags and strip_comments defaults to True.
How severe is CVE-2021-23980?: CVE-2021-23980 has a CVSS 3.x base score of 6.1, rated medium severity. It is exploitable over network with low attack complexity, requires no privileges and user interaction. Impact on confidentiality is low, integrity low, and availability none.
Is CVE-2021-23980 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (38th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2021-23980?: CVE-2021-23980 affects Mozilla Bleach. See the affected-products list for the exact vulnerable versions.
How do I fix CVE-2021-23980?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.
When was CVE-2021-23980 published?: CVE-2021-23980 was published on 2023-02-16 and last updated on 2026-06-17.

References

Affected products (1)

cpe:2.3:a:mozilla:bleach:*:*:*:*:*:*:*:*

More vulnerabilities in Mozilla Bleach

CVE-2018-7753 — Critical (CVSS 9.8): An issue was discovered in Bleach 2.1.x before 2.1.3. Attributes that have URI values weren't properly sanitized if the…
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CVE-2020-6816 — Medium (CVSS 6.1): In Mozilla Bleach before 3.12, a mutation XSS in bleach.clean when RCDATA and either svg or math tags are whitelisted…
CVE-2020-6802 — Medium (CVSS 6.1): In Mozilla Bleach before 3.11, a mutation XSS affects users calling bleach.clean with noscript and a raw tag in the…

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