What is CVE-2021-42576?

CVE-2021-42576 is a critical-severity vulnerability in Microco Bluemonday. CVSS score: 9.8/10. Published 2021-10-18.

How severe is CVE-2021-42576?

Critical severity. CVSS v3 base score is 9.8 out of 10.

Vulnerability in Microco Bluemonday

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.

Published 2021-10-18 · last modified 2026-06-17.

CVSS v3 metric

CVSS v3 base score 9.8 (Critical). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H.

EPSS exploit prediction

EPSS: 0.016 (74.3th percentile), scored 2026-09-29.

Low probability of exploitation in the next 30 days, but still tracked. 74th percentile — 74.3% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS over last 30 days · oldest: 0.016 · newest: 0.016 · change: 0.000

Affected products

References

docs.google.com/document/d/11SoX296sMS0XoQiQbpxc5pNxSdbJKDJkm5BDv0zrX50/ (Exploit, Third Party Advisory)

Frequently asked questions

What is CVE-2021-42576?: CVE-2021-42576 is a critical-severity vulnerability in Microco Bluemonday. CVSS score: 9.8/10. Published 2021-10-18.
How severe is CVE-2021-42576?: Critical severity. CVSS v3 base score is 9.8 out of 10.