6.1

CVSS Score

3.1

-

CVSS Score

Basic Information

CVE ID

CVE-2021-46871

GHSA ID

GHSA-5g2h-9x5v-5h3x

EPSS Score

0.27507%

CWE

CWE-79

Published

1/10/2023

Updated

4/6/2023

KEV Status

Technology

JavaScript

Basic Information

CVE ID

GHSA ID

EPSS Score

CWE

Published

Updated

KEV Status

Technology

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CVE-2021-46871

CVE-2021-46871: phoenix_html allows Cross-site Scripting in HEEx class attributes

tag.ex in Phoenix Phoenix.HTML (aka phoenix_html) before 3.0.4 allows XSS in HEEx class attributes

(GitHub Advisory)

Miggo Vulnerability Database

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CVE-2021-46871

CVE-2021-46871:

6.1

CVSS Score

3.1

-

CVSS Score

Basic Information

CVE ID

CVE-2021-46871

GHSA ID

GHSA-5g2h-9x5v-5h3x

EPSS Score

0.27507%

CWE

CWE-79

Published

1/10/2023

Updated

4/6/2023

KEV Status

Technology

JavaScript

Basic Information

CVE ID

GHSA ID

EPSS Score

CWE

Published

Updated

KEV Status

Technology

Technical Details

CVSS Vector

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

Package Name	Ecosystem	Vulnerable Versions	First Patched Version
phoenix_html	npm	< 3.0.4	3.0.4
phoenix_html	erlang	< 3.0.4	3.0.4

Technical Details

Vulnerability Intelligence
Miggo AI

Root Cause Analysis

The GitHub commit 62a0139 shows critical changes in tag.ex's class attribute handling:

The class_value/1 function was modified to apply attr_escape to its output
The build_attrs/1 function's logic was reordered to handle boolean attributes first, but more importantly, class list processing now flows through the escaped class_value
Test cases were added to verify escaping of dangerous characters in class attributes This indicates the root cause was missing output encoding when constructing class attribute values, which is a direct XSS vector when user-controlled data is inserted into class attributes.

Vulnerable functions

Only Mi**o us*rs **n s** t*is s**tion

WAF Protection Rules

WAF Rule

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Reasoning

*v*il**l* *or Mi**o *ustom*rs only.*v*il**l* *or Mi**o *ustom*rs only.*v*il**l* *or Mi**o *ustom*rs only.*v*il**l* *or Mi**o *ustom*rs only.*v*il**l* *or Mi**o *ustom*rs only.*v*il**l* *or Mi**o *ustom*rs only.*v*il**l* *or Mi**o *ustom*rs only.*v*il**l* *or Mi**o *ustom*rs only.*v*il**l* *or Mi**o *ustom*rs only.*v*il**l* *or Mi**o *ustom*rs only.

6.1

-

Basic Information

Basic Information

Concerned about an active attack path?

CVE-2021-46871: phoenix_html allows Cross-site Scripting in HEEx class attributes

CVE-2021-46871:

6.1

-

Basic Information

Basic Information

Technical Details

Technical Details

Vulnerability IntelligenceMiggo AI

Root Cause Analysis

Vulnerable functions

WAF Protection Rules

WAF Rule

Reasoning

Vulnerability IntelligenceMiggo AI

CVE-2021-46871: phoenix_html allows Cross-site Scripting in HEEx class attributes

6.1

6.1

Basic Information

Basic Information

Vulnerability IntelligenceMiggo AI

Root Cause Analysis

Vulnerable functions

WAF Protection Rules

WAF Rule

Reasoning

Technical Details

Vulnerability Intelligence
Miggo AI

Vulnerability Intelligence
Miggo AI

Vulnerability Intelligence
Miggo AI