How severe is CVE-2021-42576?

CVE-2021-42576 has a CVSS 3.x base score of 9.8, rated critical severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is high, integrity high, and availability high.

Is CVE-2021-42576 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 2% (71st percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2021-42576?

CVE-2021-42576 primarily affects Microco Bluemonday. In total, 2 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.

How do I fix CVE-2021-42576?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its critical severity, prioritise patching exposed systems.

When was CVE-2021-42576 published?

CVE-2021-42576 was published on 2021-10-18 and last updated on 2026-06-17.

CVE-2021-42576

CVE-2021-42576 is a critical-severity vulnerability in Microco Bluemonday with a CVSS 3.x base score of 9.8. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low.

Key facts

Severity: Critical (CVSS 3.x base score 9.8)
CVSS v2: 7.5
EPSS exploit prediction: 2% (71st percentile)
Actively exploited: Not listed in CISA KEV
Affected product: Microco Bluemonday
Published: 2021-10-18
Last modified: 2026-06-17

Description

The bluemonday sanitizer before 1.0.16 for Go, and before 0.0.8 for Python (in pybluemonday), does not properly enforce policies associated with the SELECT, STYLE, and OPTION elements.

Frequently asked questions

What is CVE-2021-42576?: The bluemonday sanitizer before 1.0.16 for Go, and before 0.0.8 for Python (in pybluemonday), does not properly enforce policies associated with the SELECT, STYLE, and OPTION elements.
How severe is CVE-2021-42576?: CVE-2021-42576 has a CVSS 3.x base score of 9.8, rated critical severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is high, integrity high, and availability high.
Is CVE-2021-42576 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 2% (71st percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2021-42576?: CVE-2021-42576 primarily affects Microco Bluemonday. In total, 2 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.
How do I fix CVE-2021-42576?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its critical severity, prioritise patching exposed systems.
When was CVE-2021-42576 published?: CVE-2021-42576 was published on 2021-10-18 and last updated on 2026-06-17.

References

https://docs.google.com/document/d/11SoX296sMS0XoQiQbpxc5pNxSdbJKDJkm5BDv0zrX50/

Affected products (2)

cpe:2.3:a:microco:bluemonday:*:*:*:*:*:go:*:*
cpe:2.3:a:python:pybluemonday:*:*:*:*:*:*:*:*

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