“Sending and receiving encrypted emails is not an easy or simple experience. Businesses rely on email with an increasing amount of sensitive data sent across their networks. A revolutionary approach that doesn’t suffer from the overheads of deployment and encryption management; just rock-solid security to give you 100% confidence in your business communications.”
During a brief crash test of the SecurEnvoy SecurMail application several severe vulnerabilities have been identified that break the core security promises of the product. These vulnerabilities open the possibility for several different attack scenarios that allow an attacker to read other users’ encrypted e-mails and overwrite or delete e-mails stored in other users’ inboxes. As we have identified several critical vulnerabilities within a very short time frame we expect numerous other vulnerabilities to be present.
As other SecureEnvoy products (besides the analyzed SecurMail) appear to be highly integrated (all products are installed with a single setup file) we suspect other components to also suffer from severe security deficits.
We recommend not to use SecurEnvoy products (especially SecurMail) in a production environment until:
- a comprehensive security audit has been performed and
- state of the art security mechanisms have been adopted.
Vulnerability Overview/ Description
- Cross Site Scripting (CVE-2018-7703, CVE-2018-7707)
SEC Consult did not find any functionality that encodes user input when creating HTML pages. Therefore persistent and reflected cross site scripting attacks are possible throughout the application. Some pages fail to properly decode URL encoded parameters. Because of this, cross site scripting cannot be exploited on these pages in most browsers.
- Path Traversal (CVE-2018-7705, CVE-2018-7706)
SEC Consult did not find any path traversal checks throughout the application. Since the application uses encrypted files as the primary method of data storage, this vulnerability can be exploited at several points. Using this vulnerability, a legitimate recipient can read mails sent to other recipients in plain text!
- Insecure Direct Object Reference (CVE-2018-7704)
Authorization checks are only partially implemented. This allows a legitimate recipient to read mails sent to other users in plain text.
- Missing Authentication and Authorization (CVE-2018-7702)
In order to send encrypted e-mails a client does not need to authenticate on the SecurEnvoy server. Therefore anyone with network access to the server can arbitrarily send e-mails that appear to come from an arbitrary sender address. Moreover, an attacker with network access to the server can re-send previous communication to arbitrary recipients. This allows him/her to extract all e-mails stored on the server. An attacker could also modify arbitrary messages stored on the server.
- Cross Site Request Forgery (CVE-2018-7701)
SEC Consult did not find any protection against cross site request forgery. An attacker could use this vulnerability to delete a victim’s e-mail or to impersonate the victim and reply to his/her e-mails.
- Cross Site Scripting (CVE-2018-7703, CVE-2018-7707)
Since these vulnerabilities were found during a very short time frame, SEC Consult believes that the product may contain a large number of other security vulnerabilities. As already several core security promises have been broken during this short crash test, no further tests were conducted.
Proof Of Concept
1) Cross Site Scripting
a) The following HTML fragments demonstrates reflected cross site scripting (CVE-2018-7703).
<form action="http://<host>/secmail/getmessage.exe" method="POST" enctype="text/plain"> <input type="hidden" name="mailboxid" value=""><script>alert('xss')</script>" /> <input type="submit" value="Submit request" /> </form>
b) E-mails that are sent using the HTML format can contain any <script> tags (CVE-2018-7707).
These are executed once the victim opens the message in the web interface.
2) Path Traversal
a) The following request demonstrates how the message body of the e-mail with id 107 can be overwritten while uploading the body for message 103. The message IDs can easily be guessed since they are assigned sequentially (CVE-2018-7705).
POST /secupload2/upload.aspx HTTP/1.1 Host: <host> Content-Type: multipart/form-data; boundary=--------822119548 Content-Length: 309 ----------822119548 Content-Disposition: form-data; name="FileName" x ----------822119548 Content-Disposition: form-data; name="MessageID" 103 ----------822119548 Content-Disposition: form-data; filename="../107/BODY" Content-Type: application/octet-stream some message ----------822119548--
b) The following link demonstrates how the message body of the e-mail with id 107 can be retrieved while only having access to the mail with id 103 (CVE-2018-7706).
3) Insecure Direct Object Reference (CVE-2018-7704)
The functionality that allows a recipient to read an e-mail checks whether the user is actually authorized to read the requested e-mail. However, by using the functionality that allows a user to reply to an e-mail, an attacker can manipulate the id that is sent as a URL parameter to read arbitrary e-mails. The following link demonstrates the retrieval of the message with id 103. The message id can easily be guessed since they are assigned sequentially.
4) Missing Authorization (CVE-2018-7702)
In order to send an e-mail to a recipient the following requests have to be made:
- Execute a GETINFO request in order to request a message id.
- Upload the message body and the attachments.
- Execute a STORE request to send the message to the recipients.
Neither of these requests require any authentication. Therefore, also no authorization is made. Attack scenarios include:
a) Extract any message by executing step #3 while specifying an own e-mail address as recipient and the message id to extract.
b) Overwrite attachments or message bodies of previously sent e-mails by executing step #2 to upload arbitrary content.
5) Cross-Site Request Forgery
SEC Consult did not find any CSRF protection within the web interface. Moreover, CSRF attacks are possible against the API used to send e-mails. Since this API does not require authentication, being authenticated on the server is not a precondition for a successful attack. Instead, the attack exploits the victim’s network location.
a) The following link demonstrates how e-mails can be deleted using a CSRF attack (CVE-2018-7701):
b) The following HTML fragment demonstrates how the API can be exploited to send an e-mail with an arbitrary message id to an arbitrary recipient (also CVE-2018-7702):
<form action="http://<host>/secserver/securectrl.exe" method="POST" enctype="text/plain"> <input type="hidden" name="FLAG:STORE VERSION:1.0 RECIPIENT_MOBILE_LIST:SMTP" value="bob@local:MOBILE=00000 SENDER:me@local RECORDED_DELIVERY: SUBJECTB64:AAAA MESSAGEID:108 SENDERMOBILE:000000 REPLY:False" /> <input type="submit" value="Submit request" /> </form>
Vulnerable / Tested Versions
The version 9.1.501 was found to be vulnerable. This was the latest version at the time of discovery.