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ProxyShell Exploit Chain

Description

ProxyShell is an exploit chain targeting on-premise installations of Microsoft Exchange Server. It was demonstrated by Orange Tsai at Pwn2Own in April 2021 and is comprised of three CVEs that, when chained, allow a remote unauthenticated attacker to execute arbitrary code on vulnerable targets. The three CVEs are CVE-2021-34473, CVE-2021-34523, and CVE-2021-31207. Details are available in Orange Tsai’s [Black Hat USA 2020 talk](<https://i.blackhat.com/USA21/Wednesday-Handouts/us-21-ProxyLogon-Is-Just-The-Tip-Of-The-Iceberg-A-New-Attack-Surface-On-Microsoft-Exchange-Server.pdf>) and follow-on [blog series](<https://blog.orange.tw/2021/08/proxylogon-a-new-attack-surface-on-ms-exchange-part-1.html>). ProxyShell is being broadly exploited in the wild as of August 12, 2021. **Recent assessments:** **ccondon-r7** at August 12, 2021 9:19pm UTC reported: Check out the [Rapid7 analysis](<https://attackerkb.com/topics/xbr3tcCFT3/proxyshell-exploit-chain/rapid7-analysis>) for details on the exploit chain. Seems like a lot of the PoC implementations so far are using admin mailboxes, but I’d imagine folks are going to start finding ways around that soon. Assessed Attacker Value: 5 Assessed Attacker Value: 5Assessed Attacker Value: 4


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