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CVE-2021-26855

Microsoft Exchange Server Remote Code Execution Vulnerability

Basic Information

CVE State: PUBLISHED
Reserved Date: February 08, 2021
Published Date: March 02, 2021
Last Updated: February 04, 2025
Vendor: Microsoft
Product: Microsoft Exchange Server 2016 Cumulative Update 19, Microsoft Exchange Server 2019 Cumulative Update 8, Microsoft Exchange Server 2019, Microsoft Exchange Server 2013 Cumulative Update 22, Microsoft Exchange Server 2019 Cumulative Update 2, Microsoft Exchange Server 2016 Cumulative Update 13, Microsoft Exchange Server 2013 Cumulative Update 23, Microsoft Exchange Server 2019 Cumulative Update 3, Microsoft Exchange Server 2016 Cumulative Update 14, Microsoft Exchange Server 2019 Cumulative Update 4, Microsoft Exchange Server 2016 Cumulative Update 15, Microsoft Exchange Server 2019 Cumulative Update 5, Microsoft Exchange Server 2019 Cumulative Update 6, Microsoft Exchange Server 2016 Cumulative Update 16, Microsoft Exchange Server 2016 Cumulative Update 17, Microsoft Exchange Server 2019 Cumulative Update 7, Microsoft Exchange Server 2016 Cumulative Update 18, Microsoft Exchange Server 2013 Cumulative Update 21, Microsoft Exchange Server 2016 Cumulative Update 12, Microsoft Exchange Server 2016 Cumulative Update 8, Microsoft Exchange Server 2019 Cumulative Update 1, Microsoft Exchange Server 2016 Cumulative Update 9, Microsoft Exchange Server 2016 Cumulative Update 10, Microsoft Exchange Server 2016 Cumulative Update 11
Description: Microsoft Exchange Server Remote Code Execution Vulnerability

CVSS Scores

CVSS v3.1

9.1 - CRITICAL

Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N/E:F/RL:O/RC:C

SSVC Information

Exploitation: active
Automatable: Yes
Technical Impact: total

Exploit Status

Exploited in the Wild: Yes (added 2021-11-03 00:00:00 UTC) Source
Proof of Concept Available: Yes (added 2021-03-23 07:37:47 UTC) Source
Used in Malware: Yes (added 2021-11-03 00:00:00 UTC) Source

References

https://portal.msrc.microsoft.com/en-US/security-guidance/advisory/CVE-2021-26855 http://packetstormsecurity.com/files/161846/Microsoft-Exchange-2019-SSRF-Arbitrary-File-Write.html http://packetstormsecurity.com/files/161938/Microsoft-Exchange-ProxyLogon-Remote-Code-Execution.html http://packetstormsecurity.com/files/162610/Microsoft-Exchange-2019-Unauthenticated-Email-Download.html http://packetstormsecurity.com/files/162736/Microsoft-Exchange-ProxyLogon-Collector.html

Known Exploited Vulnerability Information

Source	Added Date
CISA	2021-11-03 00:00:00 UTC

Scanner Integrations

Scanner	URL	Date Detected
Metasploit	https://github.com/rapid7/metasploit-framework/blob/master/modules/exploits/windows/http/exchange_proxylogon_rce.rb	2025-04-29 11:01:37 UTC
Nuclei	https://github.com/projectdiscovery/nuclei-templates/blob/main/http/cves/2021/CVE-2021-26855.yaml	2025-04-26 00:00:00 UTC

Potential Proof of Concepts

Warning: These PoCs have not been tested and could contain malware. Use at your own risk.

hictf/CVE-2021-26855-CVE-2021-27065

Type: github • Created: 2021-03-23 07:37:47 UTC • Stars: 0

analytics ProxyLogo Mail exchange RCE

catmandx/CVE-2021-26855-Exchange-RCE

Type: github • Created: 2021-03-21 06:16:24 UTC • Stars: 0

Microsoft Exchange Proxylogon Exploit Chain EXP分析

shacojx/CVE-2021-26855-exploit-Exchange

Type: github • Created: 2021-03-18 10:45:54 UTC • Stars: 6

TaroballzChen/ProxyLogon-CVE-2021-26855-metasploit

Type: github • Created: 2021-03-17 03:32:19 UTC • Stars: 4

CVE-2021-26855 proxyLogon metasploit exploit script

shacojx/Scan-Vuln-CVE-2021-26855

Type: github • Created: 2021-03-16 15:59:17 UTC • Stars: 3

Mr-xn/CVE-2021-26855-d

Type: github • Created: 2021-03-15 14:03:16 UTC • Stars: 6

ZephrFish/Exch-CVE-2021-26855_Priv

Type: github • Created: 2021-03-15 12:33:04 UTC • Stars: 4

patched to work

mil1200/ProxyLogon-CVE-2021-26855

Type: github • Created: 2021-03-14 22:57:21 UTC • Stars: 8

RCE exploit for ProxyLogon vulnerability in Microsoft Exchange

ZephrFish/Exch-CVE-2021-26855

Type: github • Created: 2021-03-14 14:23:34 UTC • Stars: 27

CVE-2021-26855: PoC (Not a HoneyPoC for once!)

KotSec/CVE-2021-26855-Scanner

Type: github • Created: 2021-03-12 12:47:41 UTC • Stars: 4

Scanner and PoC for CVE-2021-26855

hackerschoice/CVE-2021-26855

Type: github • Created: 2021-03-11 20:51:48 UTC • Stars: 61

PoC of proxylogon chain SSRF(CVE-2021-26855) to write file by testanull, censored by github

r0xdeadbeef/CVE-2021-26855

Type: github • Created: 2021-03-11 19:35:35 UTC • Stars: 12

CVE-2021-26855, also known as Proxylogon, is a server-side request forgery (SSRF) vulnerability in Exchange that allows an attacker to send arbitrary HTTP requests and authenticate as the Exchange server.