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Vulnerabilities

Vulnerability · CVE-2026-117645

Phoenix.HTML vulnerable to attribute injection via unvalidated attribute names in attributes_escape/1

Published Oct 30, 2026 · catalog updated Oct 30, 2026 · Phoenix.HTML vulnerable to attribute

Last checked Nov 6, 2026. A connected source was read within the last 7 days.

Check if you run it

No confirmed exploitation is on record for CVE-2026-117645. EPSS is 0.32%. Act only if a listed version of Phoenix.HTML vulnerable to attribute is installed.

Gaps on this record

  • The stored product name is a package slug. The name on this page is taken from the title (Phoenix.HTML vulnerable to attribute).
  • No vendor fix or required action is stored. Compare the linked advisory before you change production.
Severity
Medium5.3
Known exploitation
Not in CISA/VulnCheck KEV
EPSS
0.32%
Remediation
Not established
Affected products
Hex phoenix_html · vendor phoenixframework phoenix_html

## Summary 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 . in escapes attribute values but not attribute names. passes a binary key through , which neutralizes quotes and angle brackets but not whitespace, so a key such as ends the attribute and starts a new one. An atom key is only dasherized, so any character passes, including quotes and . Nested , and keys take the same paths. An application is affected when it builds attribute keys from untrusted input and renders them through HEEx , , or a direct call. Before 3.0.0 the same code lived in . This issue affects phoenix_html: from 1.0.0 before 3.3.5 and from 4.0.0 before 4.4.0. ## Details **1. Attribute rendering.** walks the key-value pairs through and and emits each as . Values are escaped. Names are not checked against the HTML attribute-name grammar. **2. Binary names.** sends a binary through , which replaces , , , and . Whitespace passes. HTML uses whitespace to separate attributes, so renders : a harmless attribute followed by an attacker-chosen event handler. **3. Atom names.** converts an atom with and replaces with . Nothing is escaped, so renders and renders , which leaves the tag entirely. This path needs the application to create atoms from untrusted input, for example or on a parameter. **4. Reachability.** HEEx compiles to a call to through and . and in (phoenix_html 1.x to 3.x) and in (4.x) render attributes the same way. Versions before 3.0.0 emitted the dasherized name without any escaping at all. ## Proof of concept 1. Install a vulnerable release, for example . 2. Render a binary name containing a space: returns . 3. Render an atom name containing a quote: returns . 4. Render a nested atom name: returns . 5. Place any of these maps in a HEEx template as to deliver the injected attribute to a browser. ## Impact

Are you affected?

Enter the version you run. The result uses only the ranges stored on this record.

The check returns affected, not affected, or incomplete. It does not guess a version that is missing from the record.

  • Hex phoenix_html1.0.0 → 3.3.5; 4.0.0 → 4.4.0
  • vendor phoenixframework phoenix_htmlversion unspecified

How to fix CVE-2026-117645

What to do

Three questions, each answered from this record only. Confirm the vendor advisory before you patch.

Should you patch?

No confirmed exploitation is on record for CVE-2026-117645. EPSS is 0.32%. Act only if a listed version of Phoenix.HTML vulnerable to attribute is installed.

Which versions are affected?

Compare what you have installed with 1.0.0 → 3.3.5; 4.0.0 → 4.4.0. Compare the installed version with the linked vendor advisory before you change production.

What should an analyst verify?

CWE-79: Cross-site Scripting (XSS). EPSS 0.32%. There is no CISA KEV listing. No Exploit-DB or Metasploit reference is linked. Use the source links for the original advisory.

Code

The project this record applies to. Exploit listings stay in References.

Timeline

Detection, updates, and resolution for this record.

  1. Oct 30, 2026 · OpenSSF OSV / OSV Scanner

    Detected

    ## Summary 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 . in escapes attribute values but not attribute names. passes a binary key through , which neutralizes quotes and angle brackets but not whitespace, so a

  2. Oct 30, 2026 · OpenSSF OSV / OSV Scanner

    Fix available

    phoenix_html fixed in 3.3.5; phoenix_html fixed in 4.4.0

  3. Oct 30, 2026 · OpenSSF OSV / OSV Scanner

    Fix available

    phoenix_html fixed in 3.3.5; 4.0.0

  4. Oct 30, 2026 · OpenSSF OSV / OSV Scanner

    Updated

    ## Summary 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 . in escapes attribute values but not attribute names. passes a binary key through , which neutralizes quotes and angle brackets but not whitespace, so a

Sources

  • CVE.orgVulnerability recordCVE-2026-117645

    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_

    cve.org
  • FIRST EPSSExploitation probabilityCVE-2026-117645

    30-day exploitation probability 0.32%

    first.org
  • OpenSSF OSV / OSV ScannerPackage advisoryEEF-CVE-2026-117645

    Phoenix.HTML vulnerable to attribute injection via unvalidated attribute names in attributes_escape/1

    osv.dev

References

Freshness

Last verified in this catalog Nov 6, 2026. Significant claims (KEV, EPSS, CVSS, affected ranges) come from the source rows above — open the original publisher for the authoritative advisory.

  • FIRST EPSSNov 6, 2026
  • OpenSSF OSV / OSV ScannerNov 2, 2026
  • CVE.orgOct 31, 2026