CVE-2026-33916 Handlebars.js has Prototype Pollution Leading to XSS through Partial Template Injection

Handlebars provides the power necessary to let users build semantic templates. In versions 4.0.0 through 4.7.8, resolvePartial in the Handlebars runtime resolves partial names via a plain property lookup on options.partials without guarding against prototype-chain traversal. When Object.prototype...

4coders-commons (>=0.0.1, <=0.0.2), @11ty/eleventy (0.3.3) +3663 more potentially affected by CVE-2026-33941 via handlebars (>=4.0.0, <=4.7.8)

handlebars NPM version =4.0.0, =0.0.1, =0.1.0, =0.1.0, =0.0.11, =0.0.52, =0.1.0, =0.0.72, =0.1.0, =1.1.1-pr-7-1d68cf28da, =0.0.0-13d458778df8db161111e788ed4207a13a110724, =1.16.0, =1.16.0, =1.16.0, =2.4.4 and more Source cves: CVE-2026-33941 Source advisory: SNYK:JS-HANDLEBARS-15807040...

Improper Encoding or Escaping of Output

Overview handlebars is an extension to the Mustache templating language. Affected versions of this package are vulnerable to Improper Encoding or Escaping of Output through the CLI precompiler in lib/precompiler.js. An attacker can execute arbitrary JavaScript in the generated bundle by supplying...

Handlebars.js has JavaScript Injection in CLI Precompiler via Unescaped Names and Options

Summary The Handlebars CLI precompiler bin/handlebars / lib/precompiler.js concatenates user-controlled strings — template file names and several CLI options — directly into the JavaScript it emits, without any escaping or sanitization. An attacker who can influence template filenames or CLI...

GHSA-XJPJ-3MR7-GCPF Handlebars.js has JavaScript Injection in CLI Precompiler via Unescaped Names and Options

Summary The Handlebars CLI precompiler bin/handlebars / lib/precompiler.js concatenates user-controlled strings — template file names and several CLI options — directly into the JavaScript it emits, without any escaping or sanitization. An attacker who can influence template filenames or CLI...

4coders-commons (>=0.0.1, <=0.0.2), @11ty/eleventy (0.3.3) +3663 more potentially affected by CVE-2026-33941 via handlebars (>=4.0.0, <=4.7.8)

handlebars NPM version =4.0.0, =0.0.1, =0.1.0, =0.1.0, =0.0.11, =0.0.52, =0.1.0, =0.0.72, =0.1.0, =1.1.1-pr-7-1d68cf28da, =0.0.0-13d458778df8db161111e788ed4207a13a110724, =1.16.0, =1.16.0, =1.16.0, =2.4.4 and more Source cves: CVE-2026-33941 Source advisory: OSV:GHSA-XJPJ-3MR7-GCPF...

Improper Encoding or Escaping of Output

Overview org.webjars.npm:handlebars is an extension to the Mustache templating language. Affected versions of this package are vulnerable to Improper Encoding or Escaping of Output through the CLI precompiler in lib/precompiler.js. An attacker can execute arbitrary JavaScript in the generated...

4coders-commons (>=0.0.1, <=0.0.2), @11ty/eleventy (0.3.3) +3663 more potentially affected by CVE-2026-33940 via handlebars (>=4.0.0, <=4.7.8)

handlebars NPM version =4.0.0, =0.0.1, =0.1.0, =0.1.0, =0.0.11, =0.0.52, =0.1.0, =0.0.72, =0.1.0, =1.1.1-pr-7-1d68cf28da, =0.0.0-13d458778df8db161111e788ed4207a13a110724, =1.16.0, =1.16.0, =1.16.0, =2.4.4 and more Source cves: CVE-2026-33940 Source advisory: SNYK:JS-HANDLEBARS-15803086...

Access of Resource Using Incompatible Type ('Type Confusion')

Overview org.webjars.npm:handlebars is an extension to the Mustache templating language. Affected versions of this package are vulnerable to Access of Resource Using Incompatible Type 'Type Confusion' via the resolvePartial and invokePartial functions. An attacker can execute arbitrary code on th...

GHSA-XHPV-HC6G-R9C6 Handlebars.js has JavaScript Injection via AST Type Confusion when passing an object as dynamic partial

Summary A crafted object placed in the template context can bypass all conditional guards in resolvePartial and cause invokePartial to return undefined. The Handlebars runtime then treats the unresolved partial as a source that needs to be compiled, passing the crafted object to env.compile...

Handlebars.js has JavaScript Injection via AST Type Confusion when passing an object as dynamic partial

Summary A crafted object placed in the template context can bypass all conditional guards in resolvePartial and cause invokePartial to return undefined. The Handlebars runtime then treats the unresolved partial as a source that needs to be compiled, passing the crafted object to env.compile...

4coders-commons (>=0.0.1, <=0.0.2), @11ty/eleventy (0.3.3) +3663 more potentially affected by CVE-2026-33940 via handlebars (>=4.0.0, <=4.7.8)

handlebars NPM version =4.0.0, =0.0.1, =0.1.0, =0.1.0, =0.0.11, =0.0.52, =0.1.0, =0.0.72, =0.1.0, =1.1.1-pr-7-1d68cf28da, =0.0.0-13d458778df8db161111e788ed4207a13a110724, =1.16.0, =1.16.0, =1.16.0, =2.4.4 and more Source cves: CVE-2026-33940 Source advisory: OSV:GHSA-XHPV-HC6G-R9C6...

Access of Resource Using Incompatible Type ('Type Confusion')

Overview handlebars is an extension to the Mustache templating language. Affected versions of this package are vulnerable to Access of Resource Using Incompatible Type 'Type Confusion' via the resolvePartial and invokePartial functions. An attacker can execute arbitrary code on the server by...

4coders-commons (>=0.0.1, <=0.0.2), @11ty/eleventy (0.3.3) +3663 more potentially affected by CVE-2026-33939 via handlebars (>=4.0.0, <=4.7.8)

handlebars NPM version =4.0.0, =0.0.1, =0.1.0, =0.1.0, =0.0.11, =0.0.52, =0.1.0, =0.0.72, =0.1.0, =1.1.1-pr-7-1d68cf28da, =0.0.0-13d458778df8db161111e788ed4207a13a110724, =1.16.0, =1.16.0, =1.16.0, =2.4.4 and more Source cves: CVE-2026-33939 Source advisory: SNYK:JS-HANDLEBARS-15807042...

Improper Check for Unusual or Exceptional Conditions

Overview org.webjars.npm:handlebars is an extension to the Mustache templating language. Affected versions of this package are vulnerable to Improper Check for Unusual or Exceptional Conditions through the registerDecorator path in lib/handlebars/compiler/javascript-compiler.js. An attacker can...

GHSA-9CX6-37PM-9JFF Handlebars.js has Denial of Service via Malformed Decorator Syntax in Template Compilation

Summary When a Handlebars template contains decorator syntax referencing an unregistered decorator e.g. n, the compiled template calls lookupPropertydecorators, "n", which returns undefined. The runtime then immediately invokes the result as a function, causing an unhandled TypeError: ... is not ...

4coders-commons (>=0.0.1, <=0.0.2), @11ty/eleventy (0.3.3) +3663 more potentially affected by CVE-2026-33939 via handlebars (>=4.0.0, <=4.7.8)

handlebars NPM version =4.0.0, =0.0.1, =0.1.0, =0.1.0, =0.0.11, =0.0.52, =0.1.0, =0.0.72, =0.1.0, =1.1.1-pr-7-1d68cf28da, =0.0.0-13d458778df8db161111e788ed4207a13a110724, =1.16.0, =1.16.0, =1.16.0, =2.4.4 and more Source cves: CVE-2026-33939 Source advisory: OSV:GHSA-9CX6-37PM-9JFF...

Improper Check for Unusual or Exceptional Conditions

Overview handlebars is an extension to the Mustache templating language. Affected versions of this package are vulnerable to Improper Check for Unusual or Exceptional Conditions through the registerDecorator path in lib/handlebars/compiler/javascript-compiler.js. An attacker can crash the Node.js...

Handlebars.js has Denial of Service via Malformed Decorator Syntax in Template Compilation

Summary When a Handlebars template contains decorator syntax referencing an unregistered decorator e.g. n, the compiled template calls lookupPropertydecorators, "n", which returns undefined. The runtime then immediately invokes the result as a function, causing an unhandled TypeError: ... is not ...

Handlebars.js has JavaScript Injection via AST Type Confusion by tampering @partial-block

Summary The @partial-block special variable is stored in the template data context and is reachable and mutable from within a template via helpers that accept arbitrary objects. When a helper overwrites @partial-block with a crafted Handlebars AST, a subsequent invocation of @partial-block compil...