CVE-2021-46871

phoenix_html allows Cross-site Scripting in HEEx class attributes

6.1 MediumFix available

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

Attack profile

How easy it is to exploit

Attack vector: Network
Complexity: Low
Privileges needed: None
User interaction: Required

What an attacker can affect

Confidentiality: Low
Integrity: Low
Availability: None

Exploit likelihood

0.43%Down 0.5 points since Jan 10, 2023

What each source reports

NVD Score used 6.1

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

Record: CVE-2021-46871
CVSS 3.1: 6.1 MediumCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N
Weakness: CWE-79
Updated: 2026-11-02

CVE List 6.1

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

Record: CVE-2021-46871
CVSS 3.1: 6.1 MediumCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N
Weakness: CWE-79
Updated: 2026-11-02

EUVDEUVD-2023-0339 6.1

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

Record: EUVD-2023-0339
CVSS 3.1: 6.1 MediumCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N
Updated: 2026-11-02

GitHub AdvisoriesGHSA-5g2h-9x5v-5h3x 6.1

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

Record: GHSA-5g2h-9x5v-5h3x
CVSS 3.1: 6.1 MediumCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N
Weakness: CWE-79
Updated: 2026-11-02

GitHub AdvisoriesGHSA-j3gg-r6gp-95q2 No score

XSS in HEEx class attributes

The class attribute was not protected against XSS attacks when using HEEx.

Record: GHSA-j3gg-r6gp-95q2
Weakness: CWE-79
Updated: 2026-11-02

OSV 6.1

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

Record: CVE-2021-46871
CVSS 3.1: 6.1 MediumCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N
Updated: 2026-11-02

OSVGHSA-5g2h-9x5v-5h3x 6.1

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

Record: GHSA-5g2h-9x5v-5h3x
CVSS 3.1: 6.1 MediumCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N
Weakness: CWE-79
Updated: 2026-11-02

OSVGHSA-j3gg-r6gp-95q2 No score

XSS in HEEx class attributes

The class attribute was not protected against XSS attacks when using HEEx.

Record: GHSA-j3gg-r6gp-95q2
Weakness: CWE-79
Updated: 2026-11-02

Affected products

phoenixframework phoenix html

Affected packages

Affected packages
Package	Affected	Fixed
`phoenix_html` npm	before 3.0.4	3.0.4
`phoenix_html` Hex	before 3.0.4	3.0.4
`phoenix_html` Hex	before 3.0.4, plus listed versions 1.0.01.0.11.1.01.2.01.2.1 Show 45 moreShow less 1.3.01.4.02.0.02.0.0-dev2.0.12.1.02.1.12.1.22.10.02.10.12.10.22.10.32.10.42.10.52.11.02.11.12.11.22.12.02.13.02.13.12.13.22.13.32.13.42.14.02.14.12.14.22.14.32.2.02.3.02.3.12.4.02.4.0-dev2.5.02.5.12.6.02.6.12.6.22.7.02.7.0-dev2.8.02.9.02.9.12.9.22.9.33.0.0	3.0.4

History

History
Recorded	Changed	Sources
Nov 2, 2026	first indexed	CVE List, EUVD, GitHub Advisories, NVD, OSV

Dates are when Every CVE recorded each change. Upstream dates may differ.

In short

CVE-2021-46871 is a medium vulnerability (CVSS 6.1) in Phoenixframework Phoenix Html, published April 12, 2022. No source lists public exploit code. EPSS puts the chance of exploitation in the next 30 days at 0.43%, the 37th percentile. Fixed in phoenix_html 3.0.4.

References

This page doesn't list everything

Left out here: 3 versions. The JSON record has them.