WP2SHELL Update

This morning I’ve started to see exploitation attempts on pwndefend.com (they all failed because like about 80% of sites (based on sampling) this site automatically patched, but also, this site has word fence, is fronted by Cloudflare.

Global Exposure

On the 18th (AM) I did sampling of about 3.5K hosts and found ~20% were not patched. The cyber apocalypse is not seemingly here today! (let alone the fact that if every WordPress site was popped, the world would probably not end)

CVSS Scoring is fun they said!

Ok, fun things to learn about me, I don’t like CVEs or CVSS because my brain can’t really read them! I have the same challenge with some server naming standards. I need something like SRV-UK-ADDS-01 if it’s not goy hyphens I need a tool to read them for me! (true story!). So lets look at CVSS (I know I’m full of fun topics).

I like to MoveIT MoveIT

Fast publish: If the past gives us any indication for the future, if you are running MoveIT you want to be aware of:

CVE-2026-4670 & CVE-2026-5174

Fortiweb Vulnerabilities 2025

Given the recent discovery of a critical vulnerability (CVE-2025-64446) in the Fortiweb appliances (exploitable via the management interfaces) I thought I would have a look at what other vulnerabilities have been discovered/published and what Proof of Concept (PoC) exploits exist in 2025.

Hunting for common Active Directory Domain Services Exploitations

Ok this morning I woke up really really early! I then went on a bit of a KQL thread on twitter, and then IRL work destroyed my plans to play in the lab. However I’m publishing this in its current state [use at own risk etc.] because I think it might help people! So let’s get to it:

These queries can help you identify 3 common active directory attack techniques from logs on a domain controller (this does not rely on ADCS logs etc.)

Microsoft Outlook Elevation of Privilege Vulnerability (CVE-2023-23397)

Regarding: CVE-2023-23397

This is a fast publish, use at own risk.

See guidance from Microsoft: CVE-2023-23397 – Security Update Guide – Microsoft – Microsoft Outlook Elevation of Privilege Vulnerability

If you need to mitigate the latest Outlook vulnerability which abuses an SMB/WebDav call using the Calendar invite feature you can consider the following:

CVE-2022-39952 Fortinet Global Exposure

There appears to be a new RCE out for Fortinet devices as per this post (it’s against FortiNAC as far I am aware so this is probably a much smaller exposure footprint than all fortinet devices):

https://www.fortiguard.com/psirt/FG-IR-22-300

There’s also this in FortiWeb (and well they released 40 odd fixes to various bits)

https://www.fortiguard.com/psirt/FG-IR-21-186

When we consider security edge devices and the risks these may pose to organizations and society as a whole it’s important to understand that these are no trivial matter. These are “security” appliances that are there to protect your organizations, to provide remote access as well as protect network egress etc.

Fortinet are not the only vendor to suffer from these types of vulnerability (Remote Code Execution – RCE) however there do appear to have been quite a few of these when looking historically.

ESXIArgs Vulnerable ESXi Spreadsheet

I knocked this up quickly but I “think” it’s accurate. Use at own risk etc.

ESXi-RCE-Vulnerable-Builds Download

Let me know if you find any errors/changes required etc.

Exchange Emergency Mitigation (EM) service

Yesterday I created a honeypot running Exchange 2019 in the lab. I configured very little and setup a test rule as per the MS blog to stop the SSRF from the “Autodiscover” endpoint to the Powershell function call. I put a custom response with some humour (coz why not!) but I disabled the rule:

This rule was placed in the Autodiscover virtual directory which in Exchange by default is here:

C:\Program Files\Microsoft\Exchange Server\V15\FrontEnd\HttpProxy\autodiscover\web.config

My custom rule:

<rules>

</conditions>

</rule>

</rules>

</rewrite>

This morning I checked the Honeypot, and I found the following:

Graphical user interface, text, application, email

Description automatically generated

This rule is hosted in:

C:\inetpub\wwwroot\web.config

<rules>

</conditions>

</rule>

</rules>

</rewrite>

As you can see this was modified at 03:21 01/10/2022

Graphical user interface, text, application

Description automatically generated

This comes from:

Exchange Emergency Mitigation Service (Exchange EM Service) | Microsoft Learn

“Exchange Emergency Mitigation (EM) service”

Text

Description automatically generated

You can check if this is enabled by running the following PowerShell:

Add-PSSnapin Microsoft.Exchange.Management.PowerShell.SnapIn; 

Get-OrganizationConfig | Select-Object MitigationsEnabled

So here we can see that with this enabled, the Exchange server will download and deploy the HTTP re-write rules automatically (if the server has the required version/config etc.)

You can enable or disable it with the following:

Set-OrganizationConfig -MitigationsEnabled $true
Set-OrganizationConfig -MitigationsEnabled $false

You can check this feature works using the following (modify path as required for relevent exchange version)

. "C:\Program Files\Microsoft\Exchange Server\V15\Scripts\Test-MitigationServiceConnectivity.ps1"

Check the MS docs and check your Exchange Server version to see if you have this feature etc.

GCM exsetup |%{$_.Fileversioninfo}

You learn something new everyday!

Exploitation of Microsoft Exchange Servers seen in the wild

LATEST UPDATE (04/10/2022)

The latest guidance from Microsoft (released on the 02/10/2022) says to disable administrators from being able to execute remote PowerShell via the exchange PowerShell web endpoint /PowerShell

Customer Guidance for Reported Zero-day Vulnerabilities in Microsoft Exchange Server – Microsoft Security Response Center

October 2, 2022 updates:

Added to the Mitigations section: we strongly recommend Exchange Server customers to disable remote PowerShell access for non-admin users in your organization. Guidance on how to do this for single user or multiple users is here.
Updated Detection section to refer to Analyzing attacks using the Exchange vulnerabilities CVE-2022-41040 and CVE-2022-41082.

Additional mitigations

Remove exchange web services from the internet (there are reasons to do and not do this)
Restrict hybrid servers to allow OWA to O365 only
Leverage dynamic blocking
Greynoise has a list of IPs known here: https://api.greynoise.io/v3/tags/8bf9b766-bf0f-452f-80bf-1d0903847793/ips?format=txt&token=rYZCpLOTf6UnUbBoUpF3Q

Obviously bear in mind this needs auth! but also auth isn’t always that hard..

Microsoft Research have just released (0825 30/09/2022) this: Customer Guidance for Reported Zero-day Vulnerabilities in Microsoft Exchange Server – Microsoft Security Response Center

Microsoft have released a Exchange Server Emergency Mitigation (EMS) which includes URL re-write rules to HELP mitigate this (but likely don’t eliminate all risks due to potential bypasses)

New security feature in September 2021 Cumulative Update for Exchange Server – Microsoft Tech Community

Current Scenario (Updated 11:27 30/09/2022)

Likely “Zero day” exploit in the wild being used to attack exchange servers via a simmilar endpoint to ProxyShell. A mitigation is to apply URL rewrite rules, or to disconect the service internet from untrsuted networks until a patch is available. The Exploit is reported to required AUTHENTICATION, which may significantly limit the volume of exploitation (however credentials are only a phish away). It’s also reported the exploitation in the wild used /Powershell after exploiting the autodiscover endpoint.

Overview (orginal post area)

Yesterday it was reported there was a “new” zero day vulnerability being exploited in the wild. But there appears to be some confusion and a lack of speciifc evidence to showcase the vulnerability being “new” or simply being a differnt exploit path/approach for an existing CVE (e.g. ProxyShell).

The situation from my pov (at time of writing) is still unclear. It would be odd to not advise people ensure they are running the latest supported Exchange CU and Security update release (check both!) – if the exploits are 0-day (which it looks like they are) you will need to also patch when MS release a patch!

You may also wish to: use a WAF/Web Platform (IIS or reverse proxy) to restrict access to potentially vulnreable strings/endpoints.
You should probably review vendor guidance (Microsoft)
You may want to review your exchange servers for indicators of compromise (IOCs)
Check log files for activity, Check for dropped webshells, Check process logs (if you have them!)
Microsoft Recomends using the URL re-write module see (Customer Guidance for Reported Zero-day Vulnerabilities in Microsoft Exchange Server – Microsoft Security Response Center

New Microsoft Exchange zero-days actively exploited in attacks (bleepingcomputer.com)

Upcoming | Zero Day Initiative

Warning: New attack campaign utilized a new 0-day RCE vulnerability on Microsoft Exchange Server | Blog | GTSC – Cung cấp các dịch vụ bảo mật toàn diện (gteltsc.vn)

https://www.shodan.io/search/report?query=http.title%3Aoutlook+exchange

There are 201,995 Exchange Servers with Outlook Web Access Exposed (According to Shodan)

cve-2021-31206 (19,311)
https://msrc.microsoft.com/update-guide/vulnerability/CVE-2021-31206

9.5% of the worlds Exchange attack surface is vulnerable to CVE-2021-31206

PROXYSHELL

https://www.cisa.gov/uscert/ncas/current-activity/2021/08/21/urgent-protect-against-active-exploitation-proxyshell

CVE-2021-34473 (4388)
CVE-2021-34523 (4388)
CVE-2021-31207 (4388)

2.1% of the worlds Exchange attack surface is vulnerable to ProxyShell CVEs (above) (based on the shodan data)

https://learn.microsoft.com/en-us/exchange/new-features/updates?view=exchserver-2019

Exchange CU Versions

IMPORTANT: Your NEED the LATEST Cummualative Update (CU) and the LATEST Security Updates (SU) for Exchange (and given this is a likely zero day scenario you will need to patch again when the latest patches are released from MS)

https://learn.microsoft.com/en-us/exchange/new-features/updates?view=exchserver-2019

Exchange 2019 CU12 Aug22SU

https://support.microsoft.com/en-gb/topic/description-of-the-security-update-for-microsoft-exchange-server-2019-and-2016-august-9-2022-kb5015322-86c06afb-97df-4d8f-af88-818419db8481

Exchange 2016 CU 23 Aug22SU

https://learn.microsoft.com/en-gb/Exchange/new-features/build-numbers-and-release-dates?view=exchserver-2019

https://support.microsoft.com/en-gb/topic/description-of-the-security-update-for-microsoft-exchange-server-2019-and-2016-august-9-2022-kb5015322-86c06afb-97df-4d8f-af88-818419db8481

Exchange Server 2013 CU23 Aug22SU

https://support.microsoft.com/en-gb/topic/description-of-the-security-update-for-microsoft-exchange-server-2013-august-9-2022-kb5015321-96a47598-09b7-43eb-98bb-76fdf906f265

https://www.microsoft.com/en-us/download/confirmation.aspx?id=58392

Summary

The situation appears to be evolving, as always security vulnerabilities and in the wild exploitations can be a fast moving landscape, internet facing systems need suitable and adequate protections, that doesn’t include just exposing IIS on TCP 443 and walking away. It requires capabilities such as:

WAF/CDN
DoS/DDoS Defence Considerations
Logging and Alerting
Staff to monitor and respond
Secure Configurations
Antirivurs/Antimalware
Segemntation
Endpoint Detection and Response Capabilities (EDR)
Incident Response Planning
Threat Intelligence

and many more things!

This post is a fast publish and may contain errors and/or the situation may change. I’ll try and keep it updated.