Published: 10/11/2021 Updated: 10/11/2021
CVSS v2 Base Score: 6.5 | Impact Score: 6.4 | Exploitability Score: 8
CVSS v3 Base Score: 8.8 | Impact Score: 5.9 | Exploitability Score: 2.8
Vector: AV:N/AC:L/Au:S/C:P/I:P/A:P

Vulnerability Summary

Microsoft Exchange Server Remote Code Execution Vulnerability. Exploitation Detected.

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microsoft exchange server 2016

microsoft exchange server 2019

Github Repositories

CVE-2021-42321 Microsoft Exchange Server Poc The patch:msrcmicrosoftcom/update-guide/en-US/vulnerability/CVE-2021-42321

Proxy-Attackchain proxylogon, proxyshell, proxyoracle full chain exploit tool ProxyLogon: The most well-known and impactful Exchange exploit chain ProxyOracle: The attack which could recover any password in plaintext format of Exchange users ProxyShell: The exploit chain demonstrated at Pwn2Own 2021 to take over Exchange and earn $200,000 bounty ProxyLogon is Just the Tip of

Recent Articles

Exploit released for Microsoft Exchange RCE bug, patch now
BleepingComputer • Sergiu Gatlan • 22 Nov 2021

Proof-of-concept exploit code has been released online over the weekend for an actively exploited high severity vulnerability impacting Microsoft Exchange servers.
The security bug tracked as
impacts on-premises Exchange Server 2016 and Exchange Server 2019 (including those used by customers in Exchange Hybrid mode) and was patched by Microsoft during this month's Patch Tuesday.
Successful exploitation allows authenticated attackers to execute code remotely on vulnerable Exch...

Microsoft Nov. Patch Tuesday Fixes Six Zero-Days, 55 Bugs
Threatpost • Lisa Vaas • 09 Nov 2021

Microsoft reported a total of 55 vulnerabilities, six of which are rated critical, with the remaining 49 being rated important. The flaws are found in Microsoft Windows and Windows Components, Azure, Azure RTOS, Azure Sphere, Microsoft Dynamics, Microsoft Edge (Chromium-based), Exchange Server, Microsoft Office and Office Components, Windows Hyper-V, Windows Defender, and Visual Studio.
All in all, it’s a pretty light month, according to the Zero Day Initiative’s (ZDI’s) Dustin Child...

Microsoft urges Exchange admins to patch bug exploited in the wild
BleepingComputer • Sergiu Gatlan • 09 Nov 2021

Microsoft warned admins today to immediately patch a high severity Exchange Server vulnerability that may allow authenticated attackers to execute code remotely on vulnerable servers.
The security flaw tracked as
impacts Exchange Server 2016 and Exchange Server 2019, and it is caused by improper validation of cmdlet arguments according to Redmond's security advisory.
CVE-2021-42321 only affects on-premises Microsoft Exchange servers, including those used by customers in Excha...

Let us give thanks that this November, Microsoft has given us just 55 security fixes, two of which are for actively exploited flaws
The Register • Thomas Claburn in San Francisco • 09 Nov 2021

Get our weekly newsletter Light load has infosec bods wondering what awaits next month

Patch Tuesday As the US season of giving thanks and turkey carnage approaches, let us reflect upon Microsoft's November Patch Tuesday, which has bestowed 55 CVEs and the promise of continued employment for the IT admins who have to clean up the recurring mess of software.
Only six of the vulnerabilities are considered "Critical," the rest are just "Important."
Affected applications include: 3D Viewer, Azure (including RTOS and Sphere), Dynamics, Edge, Exchange Server, Office, Power B...