Vulnerability Report

CVE-2021-26855

RCE CISA KEV Active

Title: Microsoft Exchange Server Remote Code Execution Vulnerability

RCE

Proof Of Concept

PoC Available for CVE-2021-26855

CWE Category CWE-918
Published Date Mar 03, 2021
Modified Date Oct 30, 2025
Exploit Status Available
Score 9.1 CVSS v3.1
Exploit Probability (EPSS)
100.00%

Vulnerability Summary

CVE-2021-26855: Microsoft Exchange Server Remote Code Execution Vulnerability

Impacted Vendors

M
microsoft 1

Reference Links

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 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 https://portal.msrc.microsoft.com/en-US/security-guidance/advisory/CVE-2021-26855 https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2021-26855
CVSS v3.1
Source Entity [email protected]
Severity CRITICAL
9.1
Attack Vector
NETWORK
Complexity
LOW
Privileges
N/A
Interaction
NONE
Confidentiality
N/A
Integrity
N/A
Availability
N/A
Scope
UNCHANGED
RAW VECTOR CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N
CVSS v3.1
Source Entity [email protected]
Severity CRITICAL
9.8
Attack Vector
NETWORK
Complexity
LOW
Privileges
N/A
Interaction
NONE
Confidentiality
N/A
Integrity
N/A
Availability
N/A
Scope
UNCHANGED
RAW VECTOR CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
CVSS v2.0
Source Entity [email protected]
Severity HIGH
7.5
Access Vector
N/A
Authentication
N/A
RAW VECTOR AV:N/AC:L/Au:N/C:P/I:P/A:P

Associated Attack Patterns (CAPEC)

Total: Patterns

CVE-2021-26855 Exploits & PoCs (Proof Of Concept)

Exploit-DB https://www.exploit-db.com/exploits/49663
View Code
Exploit-DB https://www.exploit-db.com/exploits/49637
View Code
Exploit-DB https://www.exploit-db.com/exploits/49879
View Code
Exploit-DB https://www.exploit-db.com/exploits/49895
View Code
MODIFIED

Vulnerability data or affected products updated.

PUBLISHED

Vulnerability first announced in NVD.

Attack Vector Matrix

Access Vector NETWORK
Complexity LOW
Privileges N/A
Interaction NONE
CVSS Vector String CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N

Affected Stack

No specific products linked.