Microsoft Points Improved Mitigations for Unpatched Alternate Server Vulnerabilities

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Microsoft on Friday disclosed it has made extra enhancements to the mitigation method supplied as a way to forestall exploitation makes an attempt in opposition to the newly disclosed unpatched safety flaws in Alternate Server.

To that finish, the tech big has revised the blocking rule in IIS Supervisor from “.*autodiscover.json.*Powershell.*” to “(?=.*autodiscover.json)(?=.*powershell).”


The record of up to date steps so as to add the URL Rewrite rule is under –

  • Open IIS Supervisor
  • Choose Default Net Web site
  • Within the Characteristic View, click on URL Rewrite
  • Within the Actions pane on the right-hand facet, click on Add Rule(s)…
  • Choose Request Blocking and click on OK
  • Add the string “(?=.*autodiscover.json)(?=.*powershell)” (excluding quotes)
  • Choose Common Expression underneath Utilizing
  • Choose Abort Request underneath How one can block after which click on OK
  • Broaden the rule and choose the rule with the sample: (?=.*autodiscover.json)(?=.*powershell) and click on Edit underneath Situations
  • Change the Situation enter from {URL} to {UrlDecode:{REQUEST_URI}} after which click on OK

Alternatively, customers can obtain the specified protections by executing a PowerShell-based Alternate On-premises Mitigation Software (EOMTv2.ps1), which has additionally been up to date to take note of the aforementioned URL sample.


The actively-exploited issues, known as ProxyNotShell (CVE-2022-41040 and CVE-2022-41082), are but to be addressed by Microsoft, though with Patch Tuesday proper across the nook, the wait is probably not for lengthy.

Profitable weaponization of the issues may allow an authenticated attacker to chain the 2 vulnerabilities to attain distant code execution on the underlying server.

The tech big, final week, acknowledged that the shortcomings could have been abused by a single state-sponsored menace actor since August 2022 in restricted focused assaults aimed toward lower than 10 organizations worldwide.

Replace: Microsoft, over the weekend, mentioned that it has as soon as once more made a correction to the URL string – “(?=.*autodiscover)(?=.*powershell)” – to be added to the blocking rule in IIS Supervisor to forestall exploitation makes an attempt.

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