CVE-2026-55760

Handlebars.java provides logic-less and semantic Mustache templates with Java. Prior to 4.5.2, applications that pass user-controlled input to Handlebars.compile() using FileTemplateLoader or ClassPathTemplateLoader are vulnerable to path traversal, allowing arbitrary file read through template names derived from URL path parameters, request parameters, or other user-controlled sources. This issue is fixed in version 4.5.2.

Handlebars.java provides logic-less and semantic Mustache templates with Java. Prior to 4.5.2, applications that pass user-controlled input to Handlebars.compile() using FileTemplateLoader or ClassPathTemplateLoader are vulnerable to path traversal, allowing arbitrary file read through template names derived from URL path parameters, request parameters, or other user-controlled sources. This issue is fixed in version 4.5.2.

Impact

Any application that passes user-controlled input to Handlebars.compile() using a FileTemplateLoader (or ClassPathTemplateLoader) is vulnerable to arbitrary file read. This is a realistic attack surface for web applications that use template names from URL path parameters, request parameters, or other user-controlled sources.

Patches

com.github.jknack:handlebars:4.5.2

Workarounds

Validate template name is derived from user input.

if (!file.getPath().startsWith(new File(prefix).getCanonicalPath())) {
        throw new IOException("Path traversal attempt detected: " + location);
}

Handlebars.java provides logic-less and semantic Mustache templates with Java. Prior to 4.5.2, applications that pass user-controlled input to Handlebars.compile() using FileTemplateLoader or ClassPathTemplateLoader are vulnerable to path traversal, allowing arbitrary file read through template names derived from URL path parameters, request parameters, or other user-controlled sources. This issue is fixed in version 4.5.2.

Handlebars.java provides logic-less and semantic Mustache templates with Java. Prior to 4.5.2, applications that pass user-controlled input to Handlebars.compile() using FileTemplateLoader or ClassPathTemplateLoader are vulnerable to path traversal, allowing arbitrary file read through template names derived from URL path parameters, request parameters, or other user-controlled sources. This issue is fixed in version 4.5.2.

Impact

Any application that passes user-controlled input to Handlebars.compile() using a FileTemplateLoader (or ClassPathTemplateLoader) is vulnerable to arbitrary file read. This is a realistic attack surface for web applications that use template names from URL path parameters, request parameters, or other user-controlled sources.

Patches

com.github.jknack:handlebars:4.5.2

Workarounds

Validate template name is derived from user input.

if (!file.getPath().startsWith(new File(prefix).getCanonicalPath())) {
        throw new IOException("Path traversal attempt detected: " + location);
}

Root has patched CVE-2026-55760 in the io.root.com.github.jknack:handlebars package for Root:Maven. Multiple fixed versions available.