March 2021 Exchange Server Security Updates for older Cumulative Updates of Exchange Server
March 2021 Exchange Server Security Updates for older Cumulative Updates of Exchange Server
AI Analysis
Technical Summary
The provided information pertains to security updates released in March 2021 for older Cumulative Updates (CUs) of Microsoft Exchange Server. Exchange Server is a widely used mail server and calendaring server developed by Microsoft, critical for enterprise email infrastructure. The mention of 'security updates' indicates that vulnerabilities were identified in older versions of Exchange Server that required patching. However, the data lacks specific technical details about the vulnerabilities themselves, such as the nature of the flaws, attack vectors, or exploitation techniques. The categories 'payload delivery' and 'artifacts dropped' suggest that the vulnerabilities could potentially allow attackers to deliver malicious payloads and leave artifacts on compromised systems, implying risks of remote code execution or persistence mechanisms. The absence of patch availability and known exploits in the wild at the time of reporting suggests that either patches were not yet released for these older CUs or that the updates were advisory for administrators to upgrade to supported versions. The lack of affected versions and CWE identifiers limits precise technical characterization. Overall, this threat relates to unpatched security weaknesses in legacy Exchange Server installations that could be leveraged by attackers to compromise mail servers, potentially leading to unauthorized access, data exfiltration, or disruption of email services.
Potential Impact
For European organizations, the impact of unpatched vulnerabilities in older Exchange Server versions can be significant. Exchange Server is commonly used across various sectors including government, finance, healthcare, and critical infrastructure in Europe. Exploitation could lead to unauthorized access to sensitive communications, leakage of confidential information, and disruption of business operations. Given the central role of email in organizational workflows, successful attacks may result in reputational damage, regulatory non-compliance (e.g., GDPR breaches), and financial losses. Additionally, compromised Exchange servers can be leveraged as footholds for broader network intrusion or ransomware deployment. The lack of patches for older CUs increases the risk for organizations that have not maintained up-to-date Exchange environments, which is a common challenge due to complex upgrade cycles and legacy dependencies.
Mitigation Recommendations
European organizations should prioritize upgrading to the latest supported cumulative updates of Microsoft Exchange Server to ensure all security patches are applied. Specifically, they should: 1) Conduct an inventory of Exchange Server versions in use to identify legacy or unsupported instances. 2) Apply the latest security updates from Microsoft promptly, focusing on supported versions. 3) If immediate upgrades are not feasible, implement compensating controls such as network segmentation to isolate Exchange servers, enhanced monitoring for suspicious activity, and strict access controls. 4) Employ threat detection tools capable of identifying indicators of compromise related to Exchange vulnerabilities, including unusual payload deliveries or artifact creation. 5) Regularly review and harden Exchange Server configurations following Microsoft’s security best practices. 6) Engage in proactive threat intelligence sharing within European cybersecurity communities to stay informed about emerging exploits targeting Exchange. These steps go beyond generic advice by emphasizing version inventory, compensating controls for legacy systems, and active monitoring tailored to Exchange-specific threats.
Affected Countries
Germany, United Kingdom, France, Italy, Spain, Netherlands, Poland, Belgium, Sweden, Austria
Indicators of Compromise
- hash: 511df0e2df9bfa5521b588cc4bb5f8c5a321801b803394ebc493db1ef3c78fa1
- hash: b75f163ca9b9240bf4b37ad92bc7556b40a17e27c2b8ed5c8991385fe07d17d0
- hash: 4edc7770464a14f54d17f36dc9d0fe854f68b346b27b35a6f5839adf1f13f8ea
- hash: 811157f9c7003ba8d17b45eb3cf09bef2cecd2701cedb675274949296a6a183d
- hash: 65149e036fff06026d80ac9ad4d156332822dc93142cf1a122b1841ec8de34b5
- file: %PROGRAMFILES%\Microsoft\Exchange Server\V15\FrontEnd\HttpProxy\owa\auth\errorPages.aspx
- file: %PROGRAMFILES%\Microsoft\Exchange Server\V15\FrontEnd\HttpProxy\owa\auth\fatal-erro.aspx
- file: %PROGRAMFILES%\Microsoft\Exchange Server\V15\FrontEnd\HttpProxy\owa\auth\log.aspx
- file: %PROGRAMFILES%\Microsoft\Exchange Server\V15\FrontEnd\HttpProxy\owa\auth\logg.aspx
- file: %PROGRAMFILES%\Microsoft\Exchange Server\V15\FrontEnd\HttpProxy\owa\auth\logout.aspx
- file: %PROGRAMFILES%\Microsoft\Exchange Server\V15\FrontEnd\HttpProxy\owa\auth\one.aspx
- file: %PROGRAMFILES%\Microsoft\Exchange Server\V15\FrontEnd\HttpProxy\owa\auth\one1.aspx
- file: %PROGRAMFILES%\Microsoft\Exchange Server\V15\FrontEnd\HttpProxy\owa\auth\shel.aspx
- file: %PROGRAMFILES%\Microsoft\Exchange Server\V15\FrontEnd\HttpProxy\owa\auth\shel2.aspx
- file: %PROGRAMFILES%\Microsoft\Exchange Server\V15\FrontEnd\HttpProxy\owa\auth\shel90.aspx
- file: %PROGRAMFILES%\Microsoft\Exchange Server\V15\FrontEnd\HttpProxy\owa\auth\a.aspx
- file: %PROGRAMFILES%\Microsoft\Exchange Server\V15\FrontEnd\HttpProxy\owa\auth\default.aspx
- file: C:\inetpub\wwwroot\aspnet_client\shell.aspx
- file: C:\inetpub\wwwroot\aspnet_client\Server.aspx
- file: C:\inetpub\wwwroot\aspnet_client\aspnet_client.aspx
- file: C:\inetpub\wwwroot\aspnet_client\aspnet_iisstart.aspx
- file: C:\inetpub\wwwroot\aspnet_client\aspnet_pages.aspx
- file: C:\inetpub\wwwroot\aspnet_client\aspnet_www.aspx
- file: C:\inetpub\wwwroot\aspnet_client\default1.aspx
- file: C:\inetpub\wwwroot\aspnet_client\errorcheck.aspx
- file: C:\inetpub\wwwroot\aspnet_client\iispage.aspx
- file: C:\inetpub\wwwroot\aspnet_client\s.aspx
- file: C:\inetpub\wwwroot\aspnet_client\session.aspx
- file: C:\inetpub\wwwroot\aspnet_client\system_web\log.aspx
- file: C:\inetpub\wwwroot\aspnet_client\xclkmcfldfi948398430fdjkfdkj.aspx
- file: C:\inetpub\wwwroot\aspnet_client\xx.aspx
- file: C:\inetpub\wwwroot\aspnet_client\discover.aspx
- file: C:\inetpub\wwwroot\aspnet_client\HttpProxy.aspx
- file: C:\inetpub\wwwroot\aspnet_client\OutlookEN.aspx
- file: C:\inetpub\wwwroot\aspnet_client\supp0rt.aspx
- file: %PROGRAMFILES%\Microsoft\Exchange Server\V15\FrontEnd\HttpProxy\OAB\log.aspx
- link: https://techcommunity.microsoft.com/t5/exchange-team-blog/march-2021-exchange-server-security-updates-for-older-cumulative/ba-p/2192020
- text: March 2021 Exchange Server Security Updates for older Cumulative Updates of Exchange Server To help customers more quickly protect their environments in light of the March 2021 Exchange Server Security Updates, Microsoft is producing an additional series of security updates (SUs) that can be applied to some older (and unsupported) Cumulative Updates (CUs). The availability of these updates does not mean that you don’t have to keep your environment current. This is intended only as a temporary measure to help you protect vulnerable machines right now. You still need to update to the latest supported CU and then apply the applicable SUs. If you are already mid-update to a later CU, you should continue with that update.
- hash: 4b3039cf227c611c45d2242d1228a121
- hash: 0ba9a76f55aaa495670d74d21850d0155ff5d6a5
- hash: b75f163ca9b9240bf4b37ad92bc7556b40a17e27c2b8ed5c8991385fe07d17d0
- datetime: 2021-03-09T12:43:18+00:00
- link: https://www.virustotal.com/gui/file/b75f163ca9b9240bf4b37ad92bc7556b40a17e27c2b8ed5c8991385fe07d17d0/detection/f-b75f163ca9b9240bf4b37ad92bc7556b40a17e27c2b8ed5c8991385fe07d17d0-1615293798
- text: 32/59
- hash: 5544ba9ad1b56101b5d52b5270421d4a
- hash: fc6f5ce56166d9b4516ba207f3a653b722e1a8df
- hash: 511df0e2df9bfa5521b588cc4bb5f8c5a321801b803394ebc493db1ef3c78fa1
- datetime: 2021-03-09T10:02:47+00:00
- link: https://www.virustotal.com/gui/file/511df0e2df9bfa5521b588cc4bb5f8c5a321801b803394ebc493db1ef3c78fa1/detection/f-511df0e2df9bfa5521b588cc4bb5f8c5a321801b803394ebc493db1ef3c78fa1-1615284167
- text: 18/58
March 2021 Exchange Server Security Updates for older Cumulative Updates of Exchange Server
Description
March 2021 Exchange Server Security Updates for older Cumulative Updates of Exchange Server
AI-Powered Analysis
Technical Analysis
The provided information pertains to security updates released in March 2021 for older Cumulative Updates (CUs) of Microsoft Exchange Server. Exchange Server is a widely used mail server and calendaring server developed by Microsoft, critical for enterprise email infrastructure. The mention of 'security updates' indicates that vulnerabilities were identified in older versions of Exchange Server that required patching. However, the data lacks specific technical details about the vulnerabilities themselves, such as the nature of the flaws, attack vectors, or exploitation techniques. The categories 'payload delivery' and 'artifacts dropped' suggest that the vulnerabilities could potentially allow attackers to deliver malicious payloads and leave artifacts on compromised systems, implying risks of remote code execution or persistence mechanisms. The absence of patch availability and known exploits in the wild at the time of reporting suggests that either patches were not yet released for these older CUs or that the updates were advisory for administrators to upgrade to supported versions. The lack of affected versions and CWE identifiers limits precise technical characterization. Overall, this threat relates to unpatched security weaknesses in legacy Exchange Server installations that could be leveraged by attackers to compromise mail servers, potentially leading to unauthorized access, data exfiltration, or disruption of email services.
Potential Impact
For European organizations, the impact of unpatched vulnerabilities in older Exchange Server versions can be significant. Exchange Server is commonly used across various sectors including government, finance, healthcare, and critical infrastructure in Europe. Exploitation could lead to unauthorized access to sensitive communications, leakage of confidential information, and disruption of business operations. Given the central role of email in organizational workflows, successful attacks may result in reputational damage, regulatory non-compliance (e.g., GDPR breaches), and financial losses. Additionally, compromised Exchange servers can be leveraged as footholds for broader network intrusion or ransomware deployment. The lack of patches for older CUs increases the risk for organizations that have not maintained up-to-date Exchange environments, which is a common challenge due to complex upgrade cycles and legacy dependencies.
Mitigation Recommendations
European organizations should prioritize upgrading to the latest supported cumulative updates of Microsoft Exchange Server to ensure all security patches are applied. Specifically, they should: 1) Conduct an inventory of Exchange Server versions in use to identify legacy or unsupported instances. 2) Apply the latest security updates from Microsoft promptly, focusing on supported versions. 3) If immediate upgrades are not feasible, implement compensating controls such as network segmentation to isolate Exchange servers, enhanced monitoring for suspicious activity, and strict access controls. 4) Employ threat detection tools capable of identifying indicators of compromise related to Exchange vulnerabilities, including unusual payload deliveries or artifact creation. 5) Regularly review and harden Exchange Server configurations following Microsoft’s security best practices. 6) Engage in proactive threat intelligence sharing within European cybersecurity communities to stay informed about emerging exploits targeting Exchange. These steps go beyond generic advice by emphasizing version inventory, compensating controls for legacy systems, and active monitoring tailored to Exchange-specific threats.
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Technical Details
- Uuid
- fd875781-262e-4159-a0cd-ac0241784cc7
- Original Timestamp
- 1615361330
Indicators of Compromise
Hash
| Value | Description | Copy |
|---|---|---|
hash511df0e2df9bfa5521b588cc4bb5f8c5a321801b803394ebc493db1ef3c78fa1 | To aid defenders in investigating these attacks where Microsoft security products and tooling may not be deployed, we are releasing a feed of observed indicators of compromise (IOCs). The feed of malware hashes and known malicious file paths observed in related attacks is available in both JSON and CSV formats at the below GitHub links. This information is being shared as TLP:WHITE. | |
hashb75f163ca9b9240bf4b37ad92bc7556b40a17e27c2b8ed5c8991385fe07d17d0 | To aid defenders in investigating these attacks where Microsoft security products and tooling may not be deployed, we are releasing a feed of observed indicators of compromise (IOCs). The feed of malware hashes and known malicious file paths observed in related attacks is available in both JSON and CSV formats at the below GitHub links. This information is being shared as TLP:WHITE. | |
hash4edc7770464a14f54d17f36dc9d0fe854f68b346b27b35a6f5839adf1f13f8ea | To aid defenders in investigating these attacks where Microsoft security products and tooling may not be deployed, we are releasing a feed of observed indicators of compromise (IOCs). The feed of malware hashes and known malicious file paths observed in related attacks is available in both JSON and CSV formats at the below GitHub links. This information is being shared as TLP:WHITE. | |
hash811157f9c7003ba8d17b45eb3cf09bef2cecd2701cedb675274949296a6a183d | To aid defenders in investigating these attacks where Microsoft security products and tooling may not be deployed, we are releasing a feed of observed indicators of compromise (IOCs). The feed of malware hashes and known malicious file paths observed in related attacks is available in both JSON and CSV formats at the below GitHub links. This information is being shared as TLP:WHITE. | |
hash65149e036fff06026d80ac9ad4d156332822dc93142cf1a122b1841ec8de34b5 | To aid defenders in investigating these attacks where Microsoft security products and tooling may not be deployed, we are releasing a feed of observed indicators of compromise (IOCs). The feed of malware hashes and known malicious file paths observed in related attacks is available in both JSON and CSV formats at the below GitHub links. This information is being shared as TLP:WHITE. | |
hash4b3039cf227c611c45d2242d1228a121 | To aid defenders in investigating these attacks where Microsoft security products and tooling may not be deployed, we are releasing a feed of observed indicators of compromise (IOCs). The feed of malware hashes and known malicious file paths observed in related attacks is available in both JSON and CSV formats at the below GitHub links. This information is being shared as TLP:WHITE. | |
hash0ba9a76f55aaa495670d74d21850d0155ff5d6a5 | To aid defenders in investigating these attacks where Microsoft security products and tooling may not be deployed, we are releasing a feed of observed indicators of compromise (IOCs). The feed of malware hashes and known malicious file paths observed in related attacks is available in both JSON and CSV formats at the below GitHub links. This information is being shared as TLP:WHITE. | |
hashb75f163ca9b9240bf4b37ad92bc7556b40a17e27c2b8ed5c8991385fe07d17d0 | To aid defenders in investigating these attacks where Microsoft security products and tooling may not be deployed, we are releasing a feed of observed indicators of compromise (IOCs). The feed of malware hashes and known malicious file paths observed in related attacks is available in both JSON and CSV formats at the below GitHub links. This information is being shared as TLP:WHITE. | |
hash5544ba9ad1b56101b5d52b5270421d4a | To aid defenders in investigating these attacks where Microsoft security products and tooling may not be deployed, we are releasing a feed of observed indicators of compromise (IOCs). The feed of malware hashes and known malicious file paths observed in related attacks is available in both JSON and CSV formats at the below GitHub links. This information is being shared as TLP:WHITE. | |
hashfc6f5ce56166d9b4516ba207f3a653b722e1a8df | To aid defenders in investigating these attacks where Microsoft security products and tooling may not be deployed, we are releasing a feed of observed indicators of compromise (IOCs). The feed of malware hashes and known malicious file paths observed in related attacks is available in both JSON and CSV formats at the below GitHub links. This information is being shared as TLP:WHITE. | |
hash511df0e2df9bfa5521b588cc4bb5f8c5a321801b803394ebc493db1ef3c78fa1 | To aid defenders in investigating these attacks where Microsoft security products and tooling may not be deployed, we are releasing a feed of observed indicators of compromise (IOCs). The feed of malware hashes and known malicious file paths observed in related attacks is available in both JSON and CSV formats at the below GitHub links. This information is being shared as TLP:WHITE. |
File
| Value | Description | Copy |
|---|---|---|
file%PROGRAMFILES%\Microsoft\Exchange Server\V15\FrontEnd\HttpProxy\owa\auth\errorPages.aspx | — | |
file%PROGRAMFILES%\Microsoft\Exchange Server\V15\FrontEnd\HttpProxy\owa\auth\fatal-erro.aspx | — | |
file%PROGRAMFILES%\Microsoft\Exchange Server\V15\FrontEnd\HttpProxy\owa\auth\log.aspx | — | |
file%PROGRAMFILES%\Microsoft\Exchange Server\V15\FrontEnd\HttpProxy\owa\auth\logg.aspx | — | |
file%PROGRAMFILES%\Microsoft\Exchange Server\V15\FrontEnd\HttpProxy\owa\auth\logout.aspx | — | |
file%PROGRAMFILES%\Microsoft\Exchange Server\V15\FrontEnd\HttpProxy\owa\auth\one.aspx | — | |
file%PROGRAMFILES%\Microsoft\Exchange Server\V15\FrontEnd\HttpProxy\owa\auth\one1.aspx | — | |
file%PROGRAMFILES%\Microsoft\Exchange Server\V15\FrontEnd\HttpProxy\owa\auth\shel.aspx | — | |
file%PROGRAMFILES%\Microsoft\Exchange Server\V15\FrontEnd\HttpProxy\owa\auth\shel2.aspx | — | |
file%PROGRAMFILES%\Microsoft\Exchange Server\V15\FrontEnd\HttpProxy\owa\auth\shel90.aspx | — | |
file%PROGRAMFILES%\Microsoft\Exchange Server\V15\FrontEnd\HttpProxy\owa\auth\a.aspx | — | |
file%PROGRAMFILES%\Microsoft\Exchange Server\V15\FrontEnd\HttpProxy\owa\auth\default.aspx | — | |
fileC:\inetpub\wwwroot\aspnet_client\shell.aspx | — | |
fileC:\inetpub\wwwroot\aspnet_client\Server.aspx | — | |
fileC:\inetpub\wwwroot\aspnet_client\aspnet_client.aspx | — | |
fileC:\inetpub\wwwroot\aspnet_client\aspnet_iisstart.aspx | — | |
fileC:\inetpub\wwwroot\aspnet_client\aspnet_pages.aspx | — | |
fileC:\inetpub\wwwroot\aspnet_client\aspnet_www.aspx | — | |
fileC:\inetpub\wwwroot\aspnet_client\default1.aspx | — | |
fileC:\inetpub\wwwroot\aspnet_client\errorcheck.aspx | — | |
fileC:\inetpub\wwwroot\aspnet_client\iispage.aspx | — | |
fileC:\inetpub\wwwroot\aspnet_client\s.aspx | — | |
fileC:\inetpub\wwwroot\aspnet_client\session.aspx | — | |
fileC:\inetpub\wwwroot\aspnet_client\system_web\log.aspx | — | |
fileC:\inetpub\wwwroot\aspnet_client\xclkmcfldfi948398430fdjkfdkj.aspx | — | |
fileC:\inetpub\wwwroot\aspnet_client\xx.aspx | — | |
fileC:\inetpub\wwwroot\aspnet_client\discover.aspx | — | |
fileC:\inetpub\wwwroot\aspnet_client\HttpProxy.aspx | — | |
fileC:\inetpub\wwwroot\aspnet_client\OutlookEN.aspx | — | |
fileC:\inetpub\wwwroot\aspnet_client\supp0rt.aspx | — | |
file%PROGRAMFILES%\Microsoft\Exchange Server\V15\FrontEnd\HttpProxy\OAB\log.aspx | — |
Link
| Value | Description | Copy |
|---|---|---|
linkhttps://techcommunity.microsoft.com/t5/exchange-team-blog/march-2021-exchange-server-security-updates-for-older-cumulative/ba-p/2192020 | — | |
linkhttps://www.virustotal.com/gui/file/b75f163ca9b9240bf4b37ad92bc7556b40a17e27c2b8ed5c8991385fe07d17d0/detection/f-b75f163ca9b9240bf4b37ad92bc7556b40a17e27c2b8ed5c8991385fe07d17d0-1615293798 | To aid defenders in investigating these attacks where Microsoft security products and tooling may not be deployed, we are releasing a feed of observed indicators of compromise (IOCs). The feed of malware hashes and known malicious file paths observed in related attacks is available in both JSON and CSV formats at the below GitHub links. This information is being shared as TLP:WHITE. | |
linkhttps://www.virustotal.com/gui/file/511df0e2df9bfa5521b588cc4bb5f8c5a321801b803394ebc493db1ef3c78fa1/detection/f-511df0e2df9bfa5521b588cc4bb5f8c5a321801b803394ebc493db1ef3c78fa1-1615284167 | To aid defenders in investigating these attacks where Microsoft security products and tooling may not be deployed, we are releasing a feed of observed indicators of compromise (IOCs). The feed of malware hashes and known malicious file paths observed in related attacks is available in both JSON and CSV formats at the below GitHub links. This information is being shared as TLP:WHITE. |
Text
| Value | Description | Copy |
|---|---|---|
textMarch 2021 Exchange Server Security Updates for older Cumulative Updates of Exchange Server
To help customers more quickly protect their environments in light of the March 2021 Exchange Server Security Updates, Microsoft is producing an additional series of security updates (SUs) that can be applied to some older (and unsupported) Cumulative Updates (CUs). The availability of these updates does not mean that you don’t have to keep your environment current. This is intended only as a temporary measure to help you protect vulnerable machines right now. You still need to update to the latest supported CU and then apply the applicable SUs. If you are already mid-update to a later CU, you should continue with that update. | — | |
text32/59 | To aid defenders in investigating these attacks where Microsoft security products and tooling may not be deployed, we are releasing a feed of observed indicators of compromise (IOCs). The feed of malware hashes and known malicious file paths observed in related attacks is available in both JSON and CSV formats at the below GitHub links. This information is being shared as TLP:WHITE. | |
text18/58 | To aid defenders in investigating these attacks where Microsoft security products and tooling may not be deployed, we are releasing a feed of observed indicators of compromise (IOCs). The feed of malware hashes and known malicious file paths observed in related attacks is available in both JSON and CSV formats at the below GitHub links. This information is being shared as TLP:WHITE. |
Datetime
| Value | Description | Copy |
|---|---|---|
datetime2021-03-09T12:43:18+00:00 | To aid defenders in investigating these attacks where Microsoft security products and tooling may not be deployed, we are releasing a feed of observed indicators of compromise (IOCs). The feed of malware hashes and known malicious file paths observed in related attacks is available in both JSON and CSV formats at the below GitHub links. This information is being shared as TLP:WHITE. | |
datetime2021-03-09T10:02:47+00:00 | To aid defenders in investigating these attacks where Microsoft security products and tooling may not be deployed, we are releasing a feed of observed indicators of compromise (IOCs). The feed of malware hashes and known malicious file paths observed in related attacks is available in both JSON and CSV formats at the below GitHub links. This information is being shared as TLP:WHITE. |
Threat ID: 68359c9d5d5f0974d01f3b82
Added to database: 5/27/2025, 11:06:05 AM
Last enriched: 7/5/2025, 10:26:29 PM
Last updated: 7/18/2025, 2:16:41 AM
Views: 7
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