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Microsoft Exchange Server Remote Code Execution Vulnerability

Microsoft Exchange Server contains an unspecified vulnerability that allows for remote code execution. This vulnerability is part of the ProxyLogon exploit chain.

Published 23 Sep 2026Updated 23 Sep 20264829 sources
CVSS 9.8 ✓ VERIFIED REFERENCE△ CISA KEV
Overview Sources History

What happened

Microsoft Exchange Server contains an unspecified vulnerability that allows for remote code execution. This vulnerability is part of the ProxyLogon exploit chain.

Affected versions

Exchange Server: See original advisory Fixed: See vendor advisory.

Why it matters

This source correlation may provide earlier visibility while structured CVE metadata is still being updated.

Detection & mitigation

  • Review the original advisory and validate affected versions.
  • Apply vendor-provided updates or mitigations when available.

Public PoC references

RepositoryAuthorFirst seenReference
Exploit-DB 49663Microsoft Exchange 2019 - Server-Side Request ForgeryF52021-03-14VerifiedExploit-DB 49637Microsoft Exchange 2019 - Server-Side Request Forgery (Proxylogon) (PoC)testanull2021-03-11VerifiedExploit-DB 49879Microsoft Exchange 2019 - Unauthenticated Email DownloadGonzalo Villegas2021-05-18VerifiedExploit-DB 49895Microsoft Exchange 2019 - Unauthenticated Email Download (Metasploit)mekhalleh2021-05-21VerifiedSploitusExploit for CVE-2021-26855 and CVE-2021-27065. CVSS 9.8.Sploitus index2026-09-23T04:55:10+00:00CandidatePoC-in-GitHub · sgnls/exchange-0days-202103IoC determination for exploitation of CVE-2021-26855, CVE-2021-26857, CVE-2021-26858 and CVE-2021-27065.★ 5sgnls2021-03-03CandidatePoC-in-GitHub · soteria-security/HAFNIUM-IOCA PowerShell script to identify indicators of exploitation of CVE-2021-26855, CVE-2021-26857, CVE-2021-26858, and CVE-2021-26865★ 22soteria-security2021-03-03CandidatePoC-in-GitHub · cert-lv/exchange_webshell_detectionDetect webshells dropped on Microsoft Exchange servers exploited through "proxylogon" group of vulnerabilites (CVE-2021-26855, CVE-2021-26857, CVE-2021-26858, CVE-2021-27065)★ 98cert-lv2021-03-05CandidatePoC-in-GitHub · conjojo/Microsoft_Exchange_Server_SSRF_CVE-2021-26855Microsoft Exchange Server SSRF漏洞(CVE-2021-26855)★ 36conjojo2021-03-06CandidatePoC-in-GitHub · pussycat0x/CVE-2021-26855-SSRFThis script helps to identify CVE-2021-26855 ssrf Poc★ 24pussycat0x2021-03-06CandidatePoC-in-GitHub · La3B0z/CVE-2021-26855-SSRF-ExchangeCVE-2021-26855 SSRF Exchange Server★ 6La3B0z2021-03-07CandidatePoC-in-GitHub · mekhalleh/exchange_proxylogonModule pack for #ProxyLogon (part. of my contribute for Metasploit-Framework) [CVE-2021-26855 && CVE-2021-27065]★ 4mekhalleh2021-03-07CandidatePoC-in-GitHub · Yt1g3r/CVE-2021-26855_SSRFPOC of CVE-2021-26855, CVE-2021-26857, CVE-2021-26858, and CVE-2021-26865, ProxyLogon poc★ 4Yt1g3r2021-03-08CandidatePoC-in-GitHub · hackerxj007/CVE-2021-26855CVE-2021-26855 exp★ 5hackerxj0072021-03-08CandidatePoC-in-GitHub · dwisiswant0/proxylogscanA fast tool to mass scan for a vulnerability on Microsoft Exchange Server that allows an attacker bypassing the authentication and impersonating as the admin (CVE-2021-26855).★ 166dwisiswant02021-03-08CandidatePoC-in-GitHub · mauricelambert/ExchangeWeaknessTestThis script test the CVE-2021-26855 vulnerability on Exchange Server.★ 0mauricelambert2021-03-09CandidatePoC-in-GitHub · DCScoder/Exchange_IOC_HunterCVE-2021-26855, CVE-2021-26857, CVE-2021-26858, CVE-2021-27065★ 0DCScoder2021-03-09CandidatePoC-in-GitHub · srvaccount/CVE-2021-26855-PoCPoC exploit code for CVE-2021-26855★ 17srvaccount2021-03-09CandidatePoC-in-GitHub · h4x0r-dz/CVE-2021-26855★ 98h4x0r-dz2021-03-09CandidatePoC-in-GitHub · alt3kx/CVE-2021-26855_PoC★ 53alt3kx2021-03-10CandidatePoC-in-GitHub · r0xDB/CVE-2021-26855CVE-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.★ 12r0xDB2021-03-11CandidatePoC-in-GitHub · hackerschoice/CVE-2021-26855PoC of proxylogon chain SSRF(CVE-2021-26855) to write file by testanull, censored by github★ 59hackerschoice2021-03-11CandidatePoC-in-GitHub · SCS-Labs/HAFNIUM-Microsoft-Exchange-0dayCVE-2021-26855, CVE-2021-26857, CVE-2021-26858, CVE-2021-27065★ 5SCS-Labs2021-03-11CandidatePoC-in-GitHub · KotSec/CVE-2021-26855-ScannerScanner and PoC for CVE-2021-26855★ 3KotSec2021-03-12CandidatePoC-in-GitHub · hakivvi/proxylogonRCE exploit for Microsoft Exchange Server (CVE-2021-26855).★ 22hakivvi2021-03-14CandidatePoC-in-GitHub · ZephrFish/Exch-CVE-2021-26855CVE-2021-26855: PoC (Not a HoneyPoC for once!)★ 28ZephrFish2021-03-14CandidatePoC-in-GitHub · mil1200/ProxyLogon-CVE-2021-26855RCE exploit for ProxyLogon vulnerability in Microsoft Exchange★ 9mil12002021-03-14CandidatePoC-in-GitHub · evilashz/ExchangeSSRFtoRCEExploitCVE-2021-26855 & CVE-2021-27065★ 28evilashz2021-03-15CandidatePoC-in-GitHub · ZephrFish/Exch-CVE-2021-26855_Privpatched to work★ 4ZephrFish2021-03-15CandidatePoC-in-GitHub · Mr-xn/CVE-2021-26855-d★ 6Mr-xn2021-03-15CandidatePoC-in-GitHub · RickGeex/ProxyLogonProxyLogon is the formally generic name for CVE-2021-26855, a vulnerability on Microsoft Exchange Server that allows an attacker bypassing the authentication and impersonating as the admin. We have also chained this bug with another post-auth arbitrary-file-write vulnerability, CVE-2021-27065, to get code execution.★ 33RickGeex2021-03-16CandidatePoC-in-GitHub · Immersive-Labs-Sec/ProxyLogonChaining CVE-2021-26855 and CVE-2021-26857 to exploit Microsoft Exchange★ 3Immersive-Labs-Sec2021-03-16CandidatePoC-in-GitHub · TaroballzChen/ProxyLogon-CVE-2021-26855-metasploitCVE-2021-26855 proxyLogon metasploit exploit script★ 4TaroballzChen2021-03-17CandidatePoC-in-GitHub · p0wershe11/ProxyLogonProxyLogon(CVE-2021-26855+CVE-2021-27065) Exchange Server RCE(SSRF->GetWebShell)★ 123p0wershe112021-03-17CandidatePoC-in-GitHub · antichown/Scan-Vuln-CVE-2021-26855★ 0antichown2021-03-18CandidatePoC-in-GitHub · catmandx/CVE-2021-26855-Exchange-RCEMicrosoft Exchange Proxylogon Exploit Chain EXP分析★ 0catmandx2021-03-21CandidatePoC-in-GitHub · hictf/CVE-2021-26855-CVE-2021-27065analytics ProxyLogo Mail exchange RCE★ 0hictf2021-03-23CandidatePoC-in-GitHub · praetorian-inc/proxylogon-exploitProof-of-concept exploit for CVE-2021-26855 and CVE-2021-27065. Unauthenticated RCE in Exchange.★ 52praetorian-inc2021-03-24CandidatePoC-in-GitHub · Flangvik/SharpProxyLogonC# POC for CVE-2021-26855 aka ProxyLogon, supports the classically semi-interactive web shell as well as shellcode injection★ 247Flangvik2021-03-29CandidatePoC-in-GitHub · haotiku/CVE-2021-26855-exploit-Exchange★ 0haotiku2021-04-14CandidatePoC-in-GitHub · hosch3n/ProxyVulns[ProxyLogon] CVE-2021-26855 & CVE-2021-27065 Fixed RawIdentity Bug Exploit. [ProxyOracle] CVE-2021-31195 & CVE-2021-31196 Exploit Chains. [ProxyShell] CVE-2021-34473 & CVE-2021-34523 & CVE-2021-31207 Exploit Chains.★ 176hosch3n2021-04-14CandidatePoC-in-GitHub · Nick-Yin12/106362522針對近期微軟公布修補遭駭客攻擊的Exchange Server漏洞問題，台灣DEVCORE表示早在1月5日便已發現安全漏洞後，並且向微軟通報此項編號命名為「CVE-2021-26855 」，以及「CVE-2021-27065」的零日漏洞，同時也將此項漏洞稱為「ProxyLogon」。 此次揭露的「ProxyLogon」漏洞，是以無需驗證即可使用的遠端程式碼執行 (Pre-Auth Remote Code Execution；Pre-Auth RCE)零日漏洞(Zero-day exploit)，可讓攻擊者得以繞過身份驗證步驟，驅使系統管理員協助執行惡意文件或執行指令，進而觸發更廣泛的攻擊。 「ProxyLogon」是微軟近期被揭露最重大的RCE漏洞之一，DEVCORE團隊遵循責任揭露 (Responsible Disclosure)原則，在發現後便第一時間立即於今年1月5日通報微軟進行修補，避免該漏洞遭有心人士利用，造成全球用戶重大損失。而微軟遂於3月2日針對相關漏洞釋出安全更新，避免用戶機敏資訊遭受惡意攻擊。個人想法:遭駭客攻擊的Exchange Server漏洞問題，台灣DEVCORE表示早在1月5日便已發現，並且向微軟通報此項編號命名為「CVE-2021-26855 」，以及「CVE-2021-27065」的零日漏洞，同時也將此項漏洞稱為「ProxyLogon」。 此次揭露的「ProxyLogon」漏洞，是以無需驗證即可使用的遠端程式碼執行 (Pre-Auth Remote Code Execution；Pre-Auth RCE)零日漏洞(Zero-day exploit)，可讓攻擊者得以繞過身份驗證步驟，驅使系統管理員協助執行惡意文件或執行指令，進而觸發更廣泛的攻擊。 「ProxyLogon」是微軟近期被揭露最重大的RCE漏洞之一，DEVCORE團隊遵循責任揭露 (Responsible Disclosure)原則，在發現後便第一時間立即於今年1月5日通報微軟進行修補，避免該漏洞遭有心人士利用，造成全球用戶重大損失。而微軟遂於3月2日針對相關漏洞釋出安全更新，避免用戶機敏資訊遭受惡意攻擊。個人想法:微軟是大眾常用的軟體之一，駭客只要察覺漏洞就會進行惡意的攻擊，微軟公布4個Exchange Server的安全漏洞後，就遭受駭客的惡意攻擊，這件事的發生，微軟需更加小心並提高資安的防護。★ 0Nick-Yin122021-04-19CandidatePoC-in-GitHub · yaoxiaoangry3/FlangvikC# POC for CVE-2021-26855 aka ProxyLogon, supports the classically semi-interactive web shell as well as shellcode in…★ 0yaoxiaoangry32021-10-30CandidatePoC-in-GitHub · thau0x01/poc_proxylogonMicrosoft Exchange ProxyLogon PoC (CVE-2021-26855)★ 8thau0x012021-12-04CandidatePoC-in-GitHub · 1342486672/FlangvikC# POC for CVE-2021-26855 aka ProxyLogon, supports the classically semi-interactive web shell as well as shellcode in…★ 013424866722022-06-07CandidatePoC-in-GitHub · kh4sh3i/ProxyLogonProxyLogon (CVE-2021-26855+CVE-2021-27065) Exchange Server RCE (SSRF->GetWebShell)★ 9kh4sh3i2022-06-27CandidatePoC-in-GitHub · wysssadda/ExchangeSmashCVE-2021-26855★ 0wysssadda2022-06-27CandidatePoC-in-GitHub · byinarie/ZirconiumTool to search for IOCs related to HAFNIUM: CVE-2021-26855 CVE-2021-26857 CVE-2021-26858 CVE-2021-27065★ 2byinarie2023-01-22CandidatePoC-in-GitHub · ssrsec/Microsoft-Exchange-RCEMicrosoft Exchange CVE-2021-26855&CVE-2021-27065★ 3ssrsec2023-02-02CandidatePoC-in-GitHub · glen-pearson/ProxyLogon-CVE-2021-26855★ 1glen-pearson2023-04-23CandidatePoC-in-GitHub · ShyTangerine/cve-2021-26855★ 0ShyTangerine2023-04-25CandidatePoC-in-GitHub · timb-machine-mirrors/testanull-CVE-2021-26855_read_poc.txtClone from gist★ 0timb-machine-mirrors2024-01-04CandidatePoC-in-GitHub · Wercd/CVE-2021-26855★ 0Wercd2025-12-04CandidatePoC-in-GitHub · SimoesCTT/CTT-ProxyLogon-RCE-v1.0---Convergent-Time-Theory-Enhanced-Microsoft-Exchange-ExploitAn advanced exploit for Microsoft Exchange Server (CVE-2021-26855, CVE-2021-27065) enhanced with Convergent Time Theory principles, achieving near-perfect theoretical rating through quantum temporal resonance and α-dispersion techniques.★ 0SimoesCTT2026-01-27CandidatePoC-in-GitHub · SimoesCTT/CTT-Exchange-RCE-v1.0---Microsoft-Exchange-Exploit-CVSS-10.0-CRITICAL-CVE-2021-26855-CVE-2021-27065CTT-enhanced version of the Microsoft Exchange Server SSRF to RCE exploit (ProxyShell/ProxyLogon), another CVSS 10.0 critical vulnerability that affected hundreds of thousands of organizations worldwide.★ 1SimoesCTT2026-01-28CandidatePoC-in-GitHub · probablysecure/Triage-CVE-2021-26855-ProxyLogon---Microsoft-Exchange-Goal is to triage well known attacks and learn how security teams quickly respond.★ 0probablysecure2026-06-29CandidateSploitusExploit for CVE-2021-26855 and CVE-2021-27065. CVSS 9.8.Sploitus index2026-10-03T08:15:30+00:00CandidateSploitusRCE exploit script for ProxyLogon (CVE-2021-26855) in Microsoft Exchange using Python 3.9.KitPloit2026-10-05T13:02:24Candidatekitploit.comRCE exploit script for ProxyLogon (CVE-2021-26855) in Microsoft Exchange using Python 3.9.ru2026-10-05T13:02:24Candidate
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