var xmlenc = require('xmlenc');

var options = {
  rsa_pub: fs.readFileSync(__dirname + '/your_rsa.pub'),
  pem: fs.readFileSync(__dirname + '/your_public_cert.pem'),
  encryptionAlgorithm: 'http://www.w3.org/2001/04/xmlenc#aes256-cbc',
  keyEncryptionAlgorighm: 'http://www.w3.org/2001/04/xmlenc#rsa-oaep-mgf1p'
};

xmlenc.encrypt('content to encrypt', options, function(err, result) {
    console.log(result);
}

<xenc:EncryptedData Type="http://www.w3.org/2001/04/xmlenc#Element" xmlns:xenc="http://www.w3.org/2001/04/xmlenc#">
  <xenc:EncryptionMethod Algorithm="http://www.w3.org/2001/04/xmlenc#aes-256-cbc" />
    <KeyInfo xmlns="http://www.w3.org/2000/09/xmldsig#">
      <e:EncryptedKey xmlns:e="http://www.w3.org/2001/04/xmlenc#">
        <e:EncryptionMethod Algorithm="http://www.w3.org/2001/04/xmlenc#rsa-oaep-mgf1p">
          <DigestMethod Algorithm="http://www.w3.org/2000/09/xmldsig#sha1" />
        </e:EncryptionMethod>
        <KeyInfo>
          <X509Data><X509Certificate>MIIEDzCCAveg... base64 cert... q3uaLvlAUo=</X509Certificate></X509Data>
        </KeyInfo>
        <e:CipherData>
          <e:CipherValue>sGH0hhzkjmLWYYY0gyQMampDM... encrypted symmetric key ...gewHMbtZafk1MHh9A==</e:CipherValue>
        </e:CipherData>
      </e:EncryptedKey>
    </KeyInfo>
    <xenc:CipherData>
        <xenc:CipherValue>V3Vb1vDl055Lp92zvK..... encrypted content.... kNzP6xTu7/L9EMAeU</xenc:CipherValue>
    </xenc:CipherData>
</xenc:EncryptedData>

var options = {
    key: fs.readFileSync(__dirname + '/your_private_key.key'),
};

xmlenc.decrypt('<xenc:EncryptedData ..... </xenc:EncryptedData>', options, function(err, result) {
    console.log(result);
}

// result

decrypted content