phoenixframework phoenix_html up to 3.3.4/4.0.0/4.3.9 Attribute Escaping lib/phoenix_html.ex Phoenix.HTML.attributes_escape cross site scripting

Summaryinfo

A vulnerability was found in phoenixframework phoenix_html up to 3.3.4/4.0.0/4.3.9 and classified as problematic. This affects the function Phoenix.HTML.attributes_escape of the file lib/phoenix_html.ex of the component Attribute Escaping. Such manipulation leads to cross site scripting. This vulnerability is listed as CVE-2026-117645. The attack may be performed from remote. There is no available exploit. It is suggested to upgrade the affected component.

Detailsinfo

A vulnerability was found in phoenixframework phoenix_html up to 3.3.4/4.0.0/4.3.9. It has been rated as problematic. Affected by this issue is the function Phoenix.HTML.attributes_escape of the file lib/phoenix_html.ex of the component Attribute Escaping. The manipulation with an unknown input leads to a cross site scripting vulnerability. Using CWE to declare the problem leads to CWE-79. The product does not neutralize or incorrectly neutralizes user-controllable input before it is placed in output that is used as a web page that is served to other users. Impacted is integrity. CVE summarizes:

Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting') vulnerability in phoenixframework phoenix_html allows an attacker who controls attribute names to inject attributes and script into rendered HTML via Phoenix.HTML.attributes_escape/1. attributes_escape/1 in lib/phoenix_html.ex escapes attribute values but not attribute names. key_escape/1 passes a binary key through html_escape, which neutralizes quotes and angle brackets but not whitespace, so a key such as x onmouseover ends the attribute and starts a new one. An atom key is only dasherized, so any character passes, including quotes and >. Nested data, aria and phx keys take the same paths. An application is affected when it builds attribute keys from untrusted input and renders them through HEEx <tag {@attrs}>, content_tag/3, or a direct call. Before 3.0.0 the same code lived in Phoenix.HTML.Tag. This issue affects phoenix_html: from 1.0.0 before 3.3.5 and from 4.0.0 before 4.4.0.

The advisory is available at cna.erlef.org. This vulnerability is handled as CVE-2026-117645 since 10/30/2026. The exploitation is known to be easy. The attack may be launched remotely. No form of authentication is required for exploitation. Successful exploitation requires user interaction by the victim. Technical details are known, but there is no available exploit. This vulnerability is assigned to T1059.007 by the MITRE ATT&CK project.

Upgrading to version 3.3.5 or 4.4.0 eliminates this vulnerability.

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Productinfo

Vendor

• phoenixframework

Name

• phoenix_html

Version

• 3.3.0
• 3.3.1
• 3.3.2
• 3.3.3
• 3.3.4
• 4.0
• 4.3.0
• 4.3.1
• 4.3.2
• 4.3.3
• 4.3.4
• 4.3.5
• 4.3.6
• 4.3.7
• 4.3.8
• 4.3.9

CPE 2.3info

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CPE 2.2info

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