gchq/CyberChef · error · Error

Schema ${error}

Error message

Schema ${error}

What it means

Thrown by Protobuf.updateProtoRoot when protobufjs `protobuf.parse(protoText)` raises an exception — the .proto text is syntactically invalid. The original parse error text is appended after 'Schema '.

Source

Thrown at src/core/lib/Protobuf.mjs:132

        this.showUnknownFields = args[1];
        this.showTypes = args[2];
        return this.mergeDecodes(input);
    }

    /**
     * Update the parsedProto, throw parsing errors
     *
     * @param {string} protoText
     */
    static updateProtoRoot(protoText) {
        try {
            this.parsedProto = protobuf.parse(protoText);
            if (this.parsedProto.package) {
                this.parsedProto.root = this.parsedProto.root.nested[this.parsedProto.package];
            }
            this.updateMainMessageName();
        } catch (error) {
            throw new Error("Schema " + error);
        }
    }

    /**
     * Set mainMessageName to the first instance of a message defined in the schema that is not a submessage
     *
     */
    static updateMainMessageName() {
        const messageNames = [];
        const fieldTypes = [];
        this.parsedProto.root.nestedArray.forEach(block => {
            if (block instanceof protobuf.Type) {
                messageNames.push(block.name);
                this.parsedProto.root.nested[block.name].fieldsArray.forEach(field => {
                    fieldTypes.push(field.type);
                });
            }
        });

View on GitHub (pinned to 4290ea7539)

Solutions

1. Read the appended protobufjs parse error for the line/column of the syntax fault.
2. Validate the .proto with `protoc --proto_path=. --descriptor_set_out=/dev/null schema.proto` or `protobuf.parse` standalone before use.
3. Ensure the schema begins with the correct `syntax` declaration.

Example fix

// before
const proto = 'message Person { string name }'; // missing semicolon
// after
const proto = 'syntax = "proto3";\nmessage Person { string name = 1; }';

try {
  protobuf.parse(protoText);
} catch (e) {
  throw new Error('Proto schema is syntactically invalid: ' + e.message);
}

function isValidProto(protoText) {
  try { protobuf.parse(protoText); return true; } catch { return false; }
}

try {
  return Protobuf.encode(input, [protoText]);
} catch (e) {
  if (/^Schema /.test(e.message)) {
    // e.message contains the protobufjs parse error with line info
  }
  throw e;
}

When it happens

Trigger: Calling encode/decode paths with a malformed .proto: missing semicolons, unbalanced braces, illegal field labels, duplicate field numbers, invalid type references, or non-protobuf text entirely.

Common situations: Hand-typed .proto with syntax errors; copy-paste truncation; using proto2 syntax features without `syntax = "proto2"`; trailing whitespace/comments breaking older protobufjs versions.

Related errors

• Schema Error: Schema not defined
• Input Error: ${error}
• Input ${error}
• Exhausted Buffer
• Unknown type 0x${type.toString(16)}

AI-assisted analysis of gchq/CyberChef@4290ea7539 (2026-08-13). Data as JSON: /api/errors/73a4b4c213218891. Report an issue: GitHub.