Known Exploited Vulnerability
9.8
CRITICAL
CVE-2021-26855
Microsoft Exchange Server Remote Code Execution Vu - [Actively Exploited]
Description

Microsoft Exchange Server Remote Code Execution Vulnerability

INFO

Published Date :

March 3, 2021, 12:15 a.m.

Last Modified :

Nov. 21, 2024, 5:56 a.m.

Source :

[email protected]

Remotely Exploitable :

Yes !

Impact Score :

5.9

Exploitability Score :

3.9
CISA Notification
CISA KEV (Known Exploited Vulnerabilities)

For the benefit of the cybersecurity community and network defenders—and to help every organization better manage vulnerabilities and keep pace with threat activity—CISA maintains the authoritative source of vulnerabilities that have been exploited in the wild.

Description :

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

Required Action :

Apply updates per vendor instructions.

Notes :

Reference CISA's ED 21-02 (https://www.cisa.gov/news-events/directives/ed-21-02-mitigate-microsoft-exchange-premises-product-vulnerabilities) for further guidance and requirements. Note: The due date for addressing this vulnerability aligns with the requirements outlined in ED 21-02. https://nvd.nist.gov/vuln/detail/CVE-2021-26855

Public PoC/Exploit Available at Github

CVE-2021-26855 has a 147 public PoC/Exploit available at Github. Go to the Public Exploits tab to see the list.

Affected Products

The following products are affected by CVE-2021-26855 vulnerability. Even if cvefeed.io is aware of the exact versions of the products that are affected, the information is not represented in the table below.

ID Vendor Product Action
1 Microsoft exchange_server
: Total Affected Vendor : 1 | Products : 1
References to Advisories, Solutions, and Tools

Here, you will find a curated list of external links that provide in-depth information, practical solutions, and valuable tools related to CVE-2021-26855.

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

We scan GitHub repositories to detect new proof-of-concept exploits. Following list is a collection of public exploits and proof-of-concepts, which have been published on GitHub (sorted by the most recently updated).

Profile Photo
vidura2/Shodan-Quest

None

Python

Updated: 1 month ago
1 stars 0 fork 0 watcher
Born at : Nov. 13, 2024, 4:54 p.m. This repo has been linked 1 different CVEs too.
Profile Photo
Coldplay1517/Middleware-Vulnerability-detection-master

中间件的exp

Updated: 2 months ago
1 stars 0 fork 0 watcher
Born at : Oct. 15, 2024, 8:49 a.m. This repo has been linked 58 different CVEs too.
Profile Photo
getanehAl/Windows-Penetration-Testing

None

PowerShell C#

Updated: 2 months ago
1 stars 0 fork 0 watcher
Born at : Oct. 11, 2024, 6:07 a.m. This repo has been linked 28 different CVEs too.
Profile Photo
ct-scorch/Security-Assessment-Findings-Report

Conducted a theoretical penetration test involving reconnaissance, vulnerability scanning, remediation, and documentation. Delivered a 15+ page technical report and 2-page executive summary. Utilized tools such as Nmap, Nessus, Netcat, OpenVAS, BurpSuite, and Wapiti.

Updated: 2 months, 3 weeks ago
0 stars 0 fork 0 watcher
Born at : Sept. 20, 2024, 4:13 p.m. This repo has been linked 7 different CVEs too.
Profile Photo
mrhili/CVE-SEARCH-NVD

None

Python

Updated: 3 months, 1 week ago
0 stars 0 fork 0 watcher
Born at : Sept. 9, 2024, 11:22 a.m. This repo has been linked 2 different CVEs too.
Profile Photo
esigiozee/Cybersecurity-Capstone-Project

None

Updated: 4 months, 1 week ago
0 stars 0 fork 0 watcher
Born at : Aug. 5, 2024, 10 p.m. This repo has been linked 3 different CVEs too.
Profile Photo
Madbat2024/Penetration-test

None

Updated: 5 months ago
0 stars 0 fork 0 watcher
Born at : July 14, 2024, 3:20 a.m. This repo has been linked 3 different CVEs too.
Profile Photo
HubTou/oab

Microsoft Exchange/Outlook Offline Address Book (.oab files) decoder

address address-book addressbook csv-export excel-export exchange json-export library microsoft oab offline offline-tool outlook servier table-export tool utility utility-library hubtools security

Makefile Python

Updated: 2 months, 3 weeks ago
0 stars 2 fork 2 watcher
Born at : June 21, 2024, 9:15 p.m. This repo has been linked 1 different CVEs too.
Profile Photo
zhoubingyan1/Golang-Learning

None

Go Smarty CSS JavaScript HTML

Updated: 6 months, 1 week ago
0 stars 0 fork 0 watcher
Born at : June 3, 2024, 7:46 a.m. This repo has been linked 9 different CVEs too.
Profile Photo
NoTsPepino/Shodan-Dorking

Lista de Shodan Dorks y herramientas para su uso

Python

Updated: 5 months, 3 weeks ago
0 stars 0 fork 0 watcher
Born at : May 24, 2024, 5:54 p.m. This repo has been linked 4 different CVEs too.
Profile Photo
naufalqwe/proxylogscan-master

None

Go

Updated: 6 months, 3 weeks ago
0 stars 0 fork 0 watcher
Born at : May 13, 2024, 12:09 a.m. This repo has been linked 2 different CVEs too.
Profile Photo
NaInSec/CVE-PoC-in-GitHub

All CVE - PoC in GitHub

poc proofofconcept tester allcve cvegithub cvenew cvepoc cveupdate

Updated: 1 month, 1 week ago
8 stars 3 fork 3 watcher
Born at : March 22, 2024, 3:58 p.m. This repo has been linked 928 different CVEs too.
Profile Photo
zecool/cve

None

Updated: 9 months ago
1 stars 0 fork 0 watcher
Born at : March 11, 2024, 1:21 p.m. This repo has been linked 930 different CVEs too.
Profile Photo
txuswashere/Cybersecurity-Handbooks

Cybersecurity-Handbooks

attack-defense cybersec cybersecurity cybersecurity-education cybersecurity-tools cybersecurity-training reconnaissance cloud cryptography forensics osint password reverse-engineering wireless wireless-security

Updated: 9 months, 2 weeks ago
1 stars 1 fork 1 watcher
Born at : Feb. 28, 2024, 10:44 a.m. This repo has been linked 4 different CVEs too.
Profile Photo
pwnlog/ALinks

Collection of links for AD purple teamers.

Updated: 3 weeks, 3 days ago
0 stars 0 fork 0 watcher
Born at : Feb. 17, 2024, 2:49 p.m. This repo has been linked 16 different CVEs too.

Results are limited to the first 15 repositories due to potential performance issues.

The following list is the news that have been mention CVE-2021-26855 vulnerability anywhere in the article.

  • The Register
Salt Typhoon's surge extends far beyond US telcos

The reach of the China-linked Salt Typhoon gang extends beyond telecommunications giants in the United States, and its arsenal includes several backdoors – including a brand-new malware dubbed GhostSp ... Read more

Published Date: Nov 27, 2024 (2 weeks, 6 days ago)
CVE-2023-48788 CVE-2024-21887 CVE-2023-46805 CVE-2022-3236 CVE-2021-27065 CVE-2021-26858 CVE-2021-26857 CVE-2021-26855
  • The Hacker News
Chinese Hackers Use GHOSTSPIDER Malware to Hack Telecoms Across 12+ Countries

The China-linked threat actor known as Earth Estries has been observed using a previously undocumented backdoor called GHOSTSPIDER as part of its attacks targeting Southeast Asian telecommunications c ... Read more

Published Date: Nov 26, 2024 (3 weeks, 1 day ago)
CVE-2023-48788 CVE-2024-21887 CVE-2023-46805 CVE-2022-3236 CVE-2021-27065 CVE-2021-26858 CVE-2021-26857 CVE-2021-26855
  • BleepingComputer
Salt Typhoon hackers backdoor telcos with new GhostSpider malware

The Chinese state-sponsored hacking group Salt Typhoon has been observed utilizing a new "GhostSpider" backdoor in attacks against telecommunication service providers. The backdoor was discovered by T ... Read more

Published Date: Nov 25, 2024 (3 weeks, 1 day ago)
CVE-2023-48788 CVE-2024-21887 CVE-2023-46805 CVE-2022-3236 CVE-2021-27065 CVE-2021-26858 CVE-2021-26857 CVE-2021-26855
  • Trend Micro
Game of Emperor: Unveiling Long Term Earth Estries Cyber Intrusions

APT & Targeted Attacks Since 2023, APT group Earth Estries has aggressively targeted key industries globally with sophisticated techniques and new backdoors, like GHOSTSPIDER and MASOL RAT, for prolon ... Read more

Published Date: Nov 25, 2024 (3 weeks, 2 days ago)
CVE-2023-48788 CVE-2024-21887 CVE-2023-46805 CVE-2022-3236 CVE-2021-27065 CVE-2021-26858 CVE-2021-26857 CVE-2021-26855
  • BleepingComputer
AT&T, Verizon reportedly hacked to target US govt wiretapping platform

Multiple U.S. broadband providers, including Verizon, AT&T, and Lumen Technologies, have been breached by a Chinese hacking group tracked as Salt Typhoon, the Wall Street Journal reports. The purpose ... Read more

Published Date: Oct 07, 2024 (2 months, 1 week ago)
CVE-2021-27065 CVE-2021-26858 CVE-2021-26857 CVE-2021-26855
  • Cybersecurity News
Researcher Identifies ToddyCat-Inspired APT Attack Leveraging ICMP Backdoor and Microsoft Exchange Flaws

Image: KasperskyCybersecurity researchers at Kaspersky’s Global Emergency Response Team (GERT) have uncovered a sophisticated attack involving an ICMP backdoor, bearing striking similarities to the ta ... Read more

Published Date: Sep 04, 2024 (3 months, 2 weeks ago)
CVE-2024-28000 CVE-2024-43360 CVE-2024-7029 CVE-2024-27182 CVE-2024-27181 CVE-2024-20419 CVE-2021-26855
  • Kaspersky
A deep dive into the most interesting incident response cases of last year

In 2023, Kaspersky’s Global Emergency Response Team (GERT) participated in services around the world that allowed our experts to gain insight into various threats and techniques used by APT groups, co ... Read more

Published Date: Sep 03, 2024 (3 months, 2 weeks ago)
CVE-2021-26855

The following table lists the changes that have been made to the CVE-2021-26855 vulnerability over time.

Vulnerability history details can be useful for understanding the evolution of a vulnerability, and for identifying the most recent changes that may impact the vulnerability's severity, exploitability, or other characteristics.

  • CVE Modified by af854a3a-2127-422b-91ae-364da2661108

    Nov. 21, 2024

    Action Type Old Value New Value
    Added Reference http://packetstormsecurity.com/files/161846/Microsoft-Exchange-2019-SSRF-Arbitrary-File-Write.html
    Added Reference http://packetstormsecurity.com/files/161938/Microsoft-Exchange-ProxyLogon-Remote-Code-Execution.html
    Added Reference http://packetstormsecurity.com/files/162610/Microsoft-Exchange-2019-Unauthenticated-Email-Download.html
    Added Reference http://packetstormsecurity.com/files/162736/Microsoft-Exchange-ProxyLogon-Collector.html
    Added Reference https://portal.msrc.microsoft.com/en-US/security-guidance/advisory/CVE-2021-26855
  • CVE Modified by [email protected]

    May. 14, 2024

    Action Type Old Value New Value
  • Modified Analysis by [email protected]

    Feb. 15, 2024

    Action Type Old Value New Value
  • CVE Modified by [email protected]

    Dec. 29, 2023

    Action Type Old Value New Value
    Changed Description Microsoft Exchange Server Remote Code Execution Vulnerability This CVE ID is unique from CVE-2021-26412, CVE-2021-26854, CVE-2021-26857, CVE-2021-26858, CVE-2021-27065, CVE-2021-27078. Microsoft Exchange Server Remote Code Execution Vulnerability
    Added CVSS V3.1 Microsoft Corporation AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N
  • CWE Remap by [email protected]

    Jul. 12, 2022

    Action Type Old Value New Value
    Changed CWE NVD-CWE-noinfo CWE-918
  • Modified Analysis by [email protected]

    May. 06, 2022

    Action Type Old Value New Value
    Changed Reference Type http://packetstormsecurity.com/files/162736/Microsoft-Exchange-ProxyLogon-Collector.html No Types Assigned http://packetstormsecurity.com/files/162736/Microsoft-Exchange-ProxyLogon-Collector.html Exploit, Third Party Advisory, VDB Entry
  • CVE Modified by [email protected]

    May. 21, 2021

    Action Type Old Value New Value
    Added Reference http://packetstormsecurity.com/files/162736/Microsoft-Exchange-ProxyLogon-Collector.html [No Types Assigned]
  • Modified Analysis by [email protected]

    May. 21, 2021

    Action Type Old Value New Value
    Changed Reference Type http://packetstormsecurity.com/files/161938/Microsoft-Exchange-ProxyLogon-Remote-Code-Execution.html Exploit, Third Party Advisory http://packetstormsecurity.com/files/161938/Microsoft-Exchange-ProxyLogon-Remote-Code-Execution.html Exploit, Third Party Advisory, VDB Entry
    Changed Reference Type http://packetstormsecurity.com/files/162610/Microsoft-Exchange-2019-Unauthenticated-Email-Download.html No Types Assigned http://packetstormsecurity.com/files/162610/Microsoft-Exchange-2019-Unauthenticated-Email-Download.html Exploit, Third Party Advisory, VDB Entry
  • CVE Modified by [email protected]

    May. 18, 2021

    Action Type Old Value New Value
    Added Reference http://packetstormsecurity.com/files/162610/Microsoft-Exchange-2019-Unauthenticated-Email-Download.html [No Types Assigned]
  • Modified Analysis by [email protected]

    Mar. 26, 2021

    Action Type Old Value New Value
    Changed Reference Type http://packetstormsecurity.com/files/161846/Microsoft-Exchange-2019-SSRF-Arbitrary-File-Write.html No Types Assigned http://packetstormsecurity.com/files/161846/Microsoft-Exchange-2019-SSRF-Arbitrary-File-Write.html Exploit, Third Party Advisory, VDB Entry
    Changed Reference Type http://packetstormsecurity.com/files/161938/Microsoft-Exchange-ProxyLogon-Remote-Code-Execution.html No Types Assigned http://packetstormsecurity.com/files/161938/Microsoft-Exchange-ProxyLogon-Remote-Code-Execution.html Exploit, Third Party Advisory
    Changed CPE Configuration OR *cpe:2.3:a:microsoft:exchange_server:2013:cumulative_update_23:*:*:*:*:*:* *cpe:2.3:a:microsoft:exchange_server:2016:cumulative_update_18:*:*:*:*:*:* *cpe:2.3:a:microsoft:exchange_server:2016:cumulative_update_19:*:*:*:*:*:* *cpe:2.3:a:microsoft:exchange_server:2019:cumulative_update_7:*:*:*:*:*:* *cpe:2.3:a:microsoft:exchange_server:2019:cumulative_update_8:*:*:*:*:*:* OR *cpe:2.3:a:microsoft:exchange_server:2013:cumulative_update_21:*:*:*:*:*:* *cpe:2.3:a:microsoft:exchange_server:2013:cumulative_update_22:*:*:*:*:*:* *cpe:2.3:a:microsoft:exchange_server:2013:cumulative_update_23:*:*:*:*:*:* *cpe:2.3:a:microsoft:exchange_server:2016:cumulative_update_10:*:*:*:*:*:* *cpe:2.3:a:microsoft:exchange_server:2016:cumulative_update_11:*:*:*:*:*:* *cpe:2.3:a:microsoft:exchange_server:2016:cumulative_update_12:*:*:*:*:*:* *cpe:2.3:a:microsoft:exchange_server:2016:cumulative_update_13:*:*:*:*:*:* *cpe:2.3:a:microsoft:exchange_server:2016:cumulative_update_14:*:*:*:*:*:* *cpe:2.3:a:microsoft:exchange_server:2016:cumulative_update_15:*:*:*:*:*:* *cpe:2.3:a:microsoft:exchange_server:2016:cumulative_update_16:*:*:*:*:*:* *cpe:2.3:a:microsoft:exchange_server:2016:cumulative_update_17:*:*:*:*:*:* *cpe:2.3:a:microsoft:exchange_server:2016:cumulative_update_18:*:*:*:*:*:* *cpe:2.3:a:microsoft:exchange_server:2016:cumulative_update_19:*:*:*:*:*:* *cpe:2.3:a:microsoft:exchange_server:2016:cumulative_update_8:*:*:*:*:*:* *cpe:2.3:a:microsoft:exchange_server:2016:cumulative_update_9:*:*:*:*:*:* *cpe:2.3:a:microsoft:exchange_server:2019:-:*:*:*:*:*:* *cpe:2.3:a:microsoft:exchange_server:2019:cumulative_update_1:*:*:*:*:*:* *cpe:2.3:a:microsoft:exchange_server:2019:cumulative_update_2:*:*:*:*:*:* *cpe:2.3:a:microsoft:exchange_server:2019:cumulative_update_3:*:*:*:*:*:* *cpe:2.3:a:microsoft:exchange_server:2019:cumulative_update_4:*:*:*:*:*:* *cpe:2.3:a:microsoft:exchange_server:2019:cumulative_update_5:*:*:*:*:*:* *cpe:2.3:a:microsoft:exchange_server:2019:cumulative_update_6:*:*:*:*:*:* *cpe:2.3:a:microsoft:exchange_server:2019:cumulative_update_7:*:*:*:*:*:* *cpe:2.3:a:microsoft:exchange_server:2019:cumulative_update_8:*:*:*:*:*:*
  • CVE Modified by [email protected]

    Mar. 23, 2021

    Action Type Old Value New Value
    Added Reference http://packetstormsecurity.com/files/161938/Microsoft-Exchange-ProxyLogon-Remote-Code-Execution.html [No Types Assigned]
  • CVE Modified by [email protected]

    Mar. 18, 2021

    Action Type Old Value New Value
    Added Reference http://packetstormsecurity.com/files/161846/Microsoft-Exchange-2019-SSRF-Arbitrary-File-Write.html [No Types Assigned]
  • Initial Analysis by [email protected]

    Mar. 09, 2021

    Action Type Old Value New Value
    Added CVSS V2 NIST (AV:N/AC:L/Au:N/C:P/I:P/A:P)
    Added CVSS V3.1 NIST AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
    Changed Reference Type https://portal.msrc.microsoft.com/en-US/security-guidance/advisory/CVE-2021-26855 No Types Assigned https://portal.msrc.microsoft.com/en-US/security-guidance/advisory/CVE-2021-26855 Patch, Vendor Advisory
    Added CWE NIST NVD-CWE-noinfo
    Added CPE Configuration OR *cpe:2.3:a:microsoft:exchange_server:2013:cumulative_update_23:*:*:*:*:*:* *cpe:2.3:a:microsoft:exchange_server:2016:cumulative_update_18:*:*:*:*:*:* *cpe:2.3:a:microsoft:exchange_server:2016:cumulative_update_19:*:*:*:*:*:* *cpe:2.3:a:microsoft:exchange_server:2019:cumulative_update_7:*:*:*:*:*:* *cpe:2.3:a:microsoft:exchange_server:2019:cumulative_update_8:*:*:*:*:*:*
EPSS is a daily estimate of the probability of exploitation activity being observed over the next 30 days. Following chart shows the EPSS score history of the vulnerability.
CWE - Common Weakness Enumeration

While CVE identifies specific instances of vulnerabilities, CWE categorizes the common flaws or weaknesses that can lead to vulnerabilities. CVE-2021-26855 is associated with the following CWEs:

Common Attack Pattern Enumeration and Classification (CAPEC)

Common Attack Pattern Enumeration and Classification (CAPEC) stores attack patterns, which are descriptions of the common attributes and approaches employed by adversaries to exploit the CVE-2021-26855 weaknesses.

Exploit Prediction

EPSS is a daily estimate of the probability of exploitation activity being observed over the next 30 days.

97.51 }} 0.01%

score

0.99991

percentile

CVSS31 - Vulnerability Scoring System
Attack Vector
Attack Complexity
Privileges Required
User Interaction
Scope
Confidentiality
Integrity
Availability
: