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CVE-2021-42576

29
FAUCET Score

CVE-2021-42576 describes a critical vulnerability in the bluemonday sanitizer for Go (before 1.0.16) and Python (before 0.0.8), where it fails to properly enforce policies for SELECT, STYLE, and OPTION HTML elements. This allows for unauthenticated remote attackers to achieve high impact on confidentiality, integrity, and availability, as indicated by its CVSS score of 9.8. Despite its critical severity, there is currently no known active exploitation, public exploit code, or significant community discussion surrounding this vulnerability.

Impacted Technologies

VendorProductVersion(s)CPE
< 1.0.16CPE matchmatch criteria
cpe:2.3:a:microco:bluemonday:*:*:*:*:*:go:*:*
< 0.0.8CPE matchmatch criteria
cpe:2.3:a:python:pybluemonday:*:*:*:*:*:*:*:*

CVSS Data

CVSS version used by this source: 3.1

9.8CRITICAL

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

Attack Vector
NETWORK
Attack Complexity
LOW
Privileges Required
NONE
User Interaction
NONE
Scope
UNCHANGED
Confidentiality Impact
HIGH
Integrity Impact
HIGH
Availability Impact
HIGH
Exploitability Score
3.9
Impact Score
5.9
CvssVersion
3.1

Exploit Intelligence

EPSS Score
1.51%
Probability of exploitation in next 30 days
EPSS Percentile
71.8%
Percentile rank of EPSS score among Peer Group
As of 2026-07-24
Model: v2026.06.15
This CVE's current EPSS score of 0.0151 is in the 59th percentile among its peer group of 36,829 CVEs.

Social Chatter

The average CVE in this peer group has 0.0 Twitter, 0.1 Reddit, 0.3 Bluesky, 0.3 Mastodon, and 2.4 GitHub mentions.

Media Mentions

No media coverage found for this CVE.

The average CVE in this peer group has 0.3 InfoSec Media, 0.0 Vendor Blog, and 0.0 Security Researcher mentions.

Remediation

Patch Available

Vendor Patches (2)

gopatch availablevia ghsa
Product: github.com/microcosm-cc/bluemondayFixed in: 1.0.16
pippatch availablevia ghsa
Product: pybluemondayFixed in: 0.0.8

Vendor Advisories (1)

pipGHSA-x95h-979x-cf3jhigh

Policies not properly enforced in bluemonday

Oct 19, 2021

References

docs.google.com / document/d/11SoX296sMS0XoQiQbpxc5pNxSdbJKDJkm5BDv0zrX50
ExploitThird Party Advisory