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    CVE-2021-26855

    Microsoft Exchange Server Remote Code Execution Vulnerability

    Published:Mar 2, 2021
    Last Modified:Aug 19, 2026
    EPS:Mar 2, 2021
    EPSS Score:0.99999
    CVSS Score:9.1

    CISA Notification

    Description

    Microsoft Exchange Server Remote Code Execution Vulnerability

    Required Action:

    Apply updates per vendor instructions.

    Notes:

    No extra notes provided.

    Due Date
    May 3, 2022
    1592 days ago
    Alert Date
    Nov 3, 2021
    1773 days ago

    Affected Products

    Vendor
    Microsoft
    Product
    Exchange Server

    Exploits

    http://packetstormsecurity.com/files/161846/Microsoft-Exchange-2019-SSRF-Arbitrary-File-Write.htmlhttp://packetstormsecurity.com/files/161938/Microsoft-Exchange-ProxyLogon-Remote-Code-Execution.htmlhttp://packetstormsecurity.com/files/162610/Microsoft-Exchange-2019-Unauthenticated-Email-Download.htmlhttp://packetstormsecurity.com/files/162736/Microsoft-Exchange-ProxyLogon-Collector.htmlhttps://www.exploit-db.com/exploits/49663https://github.com/1342486672/Flangvikhttps://github.com/alt3kx/CVE-2021-26855_PoChttps://github.com/antichown/Scan-Vuln-CVE-2021-26855https://github.com/byinarie/Zirconiumhttps://github.com/catmandx/CVE-2021-26855-Exchange-RCEhttps://github.com/cert-lv/exchange_webshell_detectionhttps://github.com/conjojo/Microsoft_Exchange_Server_SSRF_CVE-2021-26855https://github.com/DCScoder/Exchange_IOC_Hunterhttps://github.com/dwisiswant0/proxylogscanhttps://github.com/evilashz/ExchangeSSRFtoRCEExploithttps://github.com/Flangvik/SharpProxyLogonhttps://github.com/glen-pearson/ProxyLogon-CVE-2021-26855https://github.com/h4x0r-dz/CVE-2021-26855https://github.com/hackerschoice/CVE-2021-26855https://github.com/hackerxj007/CVE-2021-26855https://github.com/hakivvi/proxylogonhttps://github.com/haotiku/CVE-2021-26855-exploit-Exchangehttps://github.com/hictf/CVE-2021-26855-CVE-2021-27065https://github.com/hosch3n/ProxyVulnshttps://github.com/Immersive-Labs-Sec/ProxyLogonhttps://github.com/kh4sh3i/ProxyLogonhttps://github.com/KotSec/CVE-2021-26855-Scannerhttps://github.com/La3B0z/CVE-2021-26855-SSRF-Exchangehttps://github.com/mauricelambert/ExchangeWeaknessTesthttps://github.com/mekhalleh/exchange_proxylogonhttps://github.com/mil1200/ProxyLogon-CVE-2021-26855https://github.com/Mr-xn/CVE-2021-26855-dhttps://github.com/Nick-Yin12/106362522https://github.com/p0wershe11/ProxyLogonhttps://github.com/praetorian-inc/proxylogon-exploithttps://github.com/probablysecure/Triage-CVE-2021-26855-ProxyLogon---Microsoft-Exchange-https://github.com/pussycat0x/CVE-2021-26855-SSRFhttps://github.com/r0xDB/CVE-2021-26855https://github.com/R0XDEADBEEF/CVE-2021-26855https://github.com/RickGeex/ProxyLogonhttps://github.com/SCS-Labs/HAFNIUM-Microsoft-Exchange-0dayhttps://github.com/sgnls/exchange-0days-202103https://github.com/shacojx/CVE-2021-26855-exploit-Exchangehttps://github.com/shacojx/Scan-Vuln-CVE-2021-26855https://github.com/ShyTangerine/cve-2021-26855https://github.com/SimoesCTT/CTT-Exchange-RCE-v1.0---Microsoft-Exchange-Exploit-CVSS-10.0-CRITICAL-CVE-2021-26855-CVE-2021-27065https://github.com/SimoesCTT/CTT-ProxyLogon-RCE-v1.0---Convergent-Time-Theory-Enhanced-Microsoft-Exchange-Exploithttps://github.com/soteria-security/HAFNIUM-IOChttps://github.com/srvaccount/CVE-2021-26855-PoChttps://github.com/ssrsec/Microsoft-Exchange-RCEhttps://github.com/TaroballzChen/ProxyLogon-CVE-2021-26855-metasploithttps://github.com/thau0x01/poc_proxylogonhttps://github.com/TheDudeD6/ExchangeSmashhttps://github.com/timb-machine-mirrors/testanull-CVE-2021-26855_read_poc.txthttps://github.com/Wercd/CVE-2021-26855https://github.com/wysssadda/ExchangeSmashhttps://github.com/yaoxiaoangry3/Flangvikhttps://github.com/Yt1g3r/CVE-2021-26855_SSRFhttps://github.com/ZephrFish/Exch-CVE-2021-26855https://github.com/ZephrFish/Exch-CVE-2021-26855_Privhttps://www.exploit-db.com/exploits/49637https://www.exploit-db.com/exploits/49879https://www.exploit-db.com/exploits/49895

    Common Attack Pattern Enumeration and Classification (CAPEC)

    CAPEC-664 Server Side Request Forgery

    Related CVEs

    CVE-2026-62911 (CVSS 8) — Authentication bypass by capture-replay in Microsoft Exchange Server allows an authorized attacker to elevate …
    CVE-2026-65813 (CVSS 6.5) — Server-side request forgery (ssrf) in Microsoft Exchange Server allows an authorized attacker to elevate privi…
    CVE-2026-62915 (CVSS 6.5) — Missing authorization in Microsoft Exchange Server allows an authorized attacker to bypass a security feature …
    CVE-2026-62914 (CVSS 7.3) — Improper neutralization of input during web page generation ('cross-site scripting') in Microsoft Exchange Ser…
    CVE-2026-62913 (CVSS 8.8) — Heap-based buffer overflow in Microsoft Exchange Server allows an authorized attacker to execute code over a n…
    CVE-2026-62912 (CVSS 6.5) — Deserialization of untrusted data in Microsoft Exchange Server allows an authorized attacker to deny service o…
    CVE-2026-62910 (CVSS 7.2) — Improper control of resource identifiers ('resource injection') in Microsoft Exchange Server allows an authori…
    CVE-2026-47631 (CVSS 8.1) — Improper neutralization of input during web page generation ('cross-site scripting') in Microsoft Exchange Ser…
    CVE-2026-45504 (CVSS 8.8) — Server-side request forgery (ssrf) in Microsoft Exchange Server allows an authorized attacker to elevate privi…
    CVE-2026-45503 (CVSS 8.1) — Improper authorization in Microsoft Exchange Server allows an authorized attacker to disclose information over…

    Common Vulnerability Scoring System

    Attack Vector
    Network
    Adjacent
    Local
    Physical
    Privileges Required
    None
    Low
    High
    User Interaction
    None
    Required
    Scope
    Unchanged
    Changed
    Confidentiality
    None
    Low
    High
    Integrity
    None
    Low
    High
    Availability
    None
    Low
    High