CVE-2021-28480
published 2021-04-13CVE-2021-28480: Microsoft Exchange Server Remote Code Execution Vulnerability
PriorityP181critical9.8CVSS 3.1
AVNACLPRNUINSUCHIHAH
EXPLOIT
EPSS
71.43%
99.3th percentile
Microsoft Exchange Server Remote Code Execution Vulnerability
Affected
14 ranges
| Vendor | Product | Version range | Fixed in |
|---|---|---|---|
| jointjs | jointjs | >= 0 < 3.4.2 | 3.4.2 |
| microsoft | exchange_server | — | — |
| microsoft | exchange_server | — | — |
| microsoft | exchange_server | — | — |
| microsoft | microsoft_exchange_server_2013_cumulative_update_23 | >= 15.00.0 < 15.00.1497.015 | 15.00.1497.015 |
| microsoft | microsoft_exchange_server_2016_cumulative_update_19 | >= 15.01.0 < 15.01.2176.012 | 15.01.2176.012 |
| microsoft | microsoft_exchange_server_2016_cumulative_update_20 | >= 15.01.0 < 15.01.2242.008 | 15.01.2242.008 |
| microsoft | microsoft_exchange_server_2019_cumulative_update_8 | >= 15.02.0 < 15.02.0792.013 | 15.02.0792.013 |
| microsoft | microsoft_exchange_server_2019_cumulative_update_9 | >= 15.02.0 < 15.02.0858.010 | 15.02.0858.010 |
| msrc | microsoft_exchange_server_2013_cumulative_update_23 | — | — |
| msrc | microsoft_exchange_server_2016_cumulative_update_19 | — | — |
| msrc | microsoft_exchange_server_2016_cumulative_update_20 | — | — |
| msrc | microsoft_exchange_server_2019_cumulative_update_8 | — | — |
| msrc | microsoft_exchange_server_2019_cumulative_update_9 | — | — |
Detection & IOCsextracted from sources · hover to see the quote
cookieX-BackEndCookie={{email}}={{base64(hex_decode(rawXor))}}
path/owa/calendar/{{randstr}}
otherhttp.favicon.hash:1768726119
snort↗
SID 57403
snort↗
SID 57404
snort↗
SID 57411
snort↗
SID 57414
yara
words: ["NT+AUTHORITY", "Microsoft.Exchange.Clients.Owa2.Server.Core.OwaADUserNotFoundException"]
- →Exploit probe sends GET request to /owa/ and extracts the X-FEServer response header to identify the backend server name for subsequent SSRF/ACL bypass requests. ↗
- →The exploit constructs a malicious X-BackEndCookie by XOR-encoding a crafted string (containing server name, port 444, and OWA path) with 0xFF and base64-encoding the result, then sends it with the X-AnchorMailbox header to trigger the SSRF/ACL bypass.
- →Successful exploitation is indicated by the response body containing both 'NT+AUTHORITY' and 'Microsoft.Exchange.Clients.Owa2.Server.Core.OwaADUserNotFoundException' with HTTP 302 status.
- →Shodan/FOFA queries for exposed Exchange servers (potential targets): favicon hash 1768726119 or title 'outlook'.
- →The vulnerability is a Pre-Auth SSRF / ACL Bypass (ProxyNotFound) in Microsoft Exchange Server requiring only network access — no authentication needed.
- ·The Snort SIDs 57403, 57404, 57411, and 57414 cover the broader set of four Exchange RCE CVEs (CVE-2021-28480 through CVE-2021-28483) disclosed in the same Patch Tuesday; individual SID-to-CVE mapping is not specified in the source. ↗
- ·At time of Microsoft's advisory publication, exploit status was 'Publicly Disclosed: No; Exploited: No' but rated 'Exploitation More Likely' for both latest and older software releases. ↗
CVSS provenance
nvdv3.19.8CRITICALCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
nvdv2.010.0CRITICALAV:N/AC:L/Au:N/C:C/I:C/A:C
ghsa9.8CRITICAL
vendor_msrc9.8CRITICAL
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Every Monday: what got weaponized or added to CISA KEV in the last seven days — each CVE cross-linked to its PoC, Nuclei template, and detection rule. Free, one email a week, unsubscribe in one click.
GHSA
GHSA-hj49-fxwm-2v87: Microsoft Exchange Server Remote Code Execution Vulnerability This CVE ID is unique from CVE-2021-28480, CVE-2021-28482, CVE-2021-28483
ghsa_unreviewed·2022-05-24·CVSS 9.8
CVE-2021-28481 [CRITICAL] GHSA-hj49-fxwm-2v87: Microsoft Exchange Server Remote Code Execution Vulnerability This CVE ID is unique from CVE-2021-28480, CVE-2021-28482, CVE-2021-28483
Microsoft Exchange Server Remote Code Execution Vulnerability This CVE ID is unique from CVE-2021-28480, CVE-2021-28482, CVE-2021-28483.
GHSA
GHSA-r36c-4fw5-xj49: Microsoft Exchange Server Remote Code Execution Vulnerability This CVE ID is unique from CVE-2021-28480, CVE-2021-28481, CVE-2021-28482
ghsa_unreviewed·2022-05-24·CVSS 9.8
CVE-2021-28483 [CRITICAL] GHSA-r36c-4fw5-xj49: Microsoft Exchange Server Remote Code Execution Vulnerability This CVE ID is unique from CVE-2021-28480, CVE-2021-28481, CVE-2021-28482
Microsoft Exchange Server Remote Code Execution Vulnerability This CVE ID is unique from CVE-2021-28480, CVE-2021-28481, CVE-2021-28482.
GHSA
GHSA-5w74-wv2v-34cm: Microsoft Exchange Server Remote Code Execution Vulnerability This CVE ID is unique from CVE-2021-28480, CVE-2021-28481, CVE-2021-28483
ghsa_unreviewed·2022-05-24·CVSS 9.8
CVE-2021-28482 [CRITICAL] GHSA-5w74-wv2v-34cm: Microsoft Exchange Server Remote Code Execution Vulnerability This CVE ID is unique from CVE-2021-28480, CVE-2021-28481, CVE-2021-28483
Microsoft Exchange Server Remote Code Execution Vulnerability This CVE ID is unique from CVE-2021-28480, CVE-2021-28481, CVE-2021-28483.
GHSA
GHSA-g7vr-3jq4-gwf3: Microsoft Exchange Server Remote Code Execution Vulnerability This CVE ID is unique from CVE-2021-28481, CVE-2021-28482, CVE-2021-28483
ghsa_unreviewed·2022-05-24·CVSS 9.8
CVE-2021-28480 [CRITICAL] GHSA-g7vr-3jq4-gwf3: Microsoft Exchange Server Remote Code Execution Vulnerability This CVE ID is unique from CVE-2021-28481, CVE-2021-28482, CVE-2021-28483
Microsoft Exchange Server Remote Code Execution Vulnerability This CVE ID is unique from CVE-2021-28481, CVE-2021-28482, CVE-2021-28483.
GHSA
Prototype Pollution in jointjs
ghsa·2021-09-22·CVSS 9.8
CVE-2021-23444 [HIGH] CWE-1321 Prototype Pollution in jointjs
Prototype Pollution in jointjs
This affects the package jointjs before 3.4.2. A type confusion vulnerability can lead to a bypass of CVE-2020-28480 when the user-provided keys used in the path parameter are arrays in the setByPath function.
Microsoft
Microsoft Exchange Server Remote Code Execution Vulnerability
vendor_msrc·2021-04-13·CVSS 9.8
CVE-2021-28480 [CRITICAL] Microsoft Exchange Server Remote Code Execution Vulnerability
Microsoft Exchange Server Remote Code Execution Vulnerability
FAQ: Where can I find more information about protecting myself from this vulnerability?
Please see the MSRC Blog Post April 2021 Update Tuesday packages now available for more information.
Microsoft Exchange Server: Microsoft Exchange Server
Microsoft: Microsoft
Impact: Remote Code Execution
Exploit Status: Publicly Disclosed:No;Exploited:No;Latest Software Release:Exploitation More Likely;Older Software Release:Exploitation More Likely;DOS:N/A
Reference: http://www.microsoft.com/download/details.aspx?familyid=f827ff3b-194c-4470-aa8f-6cedc0d95d07
Reference: https://support.microsoft.com/help/5001779
Reference: http://www.microsoft.com/download/details.aspx?familyid=52da6d67-e0c4-4af0-a133-1e47217b6309
Reference: http://
No detection rules found.
Nuclei
Microsoft Exchange - Pre-Auth SSRF / ACL Bypass (ProxyNotFound)
nuclei·CVSS 9.8
CVE-2021-28480 [CRITICAL] Microsoft Exchange - Pre-Auth SSRF / ACL Bypass (ProxyNotFound)
Microsoft Exchange - Pre-Auth SSRF / ACL Bypass (ProxyNotFound)
Microsoft Exchange Server contains a remote code execution caused by improper input validation in the server component, letting remote attackers execute arbitrary code, exploit requires network access to the server.
Template:
id: CVE-2021-28480
info:
name: Microsoft Exchange - Pre-Auth SSRF / ACL Bypass (ProxyNotFound)
author: daffainfo
severity: critical
description: |
Microsoft Exchange Server contains a remote code execution caused by improper input validation in the server component, letting remote attackers execute arbitrary code, exploit requires network access to the server.
impact: |
Attackers can execute arbitrary code remotely, potentially leading to full system compromise or data breach
remediation: |
Apply the
Talos
Threat Source Newsletter (April 15, 2021)
blogs_talos·2021-04-15
Threat Source Newsletter (April 15, 2021)
Newsletter compiled by Jon Munshaw.
Good afternoon, Talos readers.
If you missed our webinar last week, we've got you covered. We've uploaded an extended version to our YouTube page that includes the scripts used in the presentation. This video will show you how to reverse-engineer and detect Android malware.
We also had Patch Tuesday this week, which featured some more vulnerabilities in Microsoft Exchange Server. Here is a full breakdown of the issues you should know about and Snort rules to keep users protected from exploitation. Cisco Talos researchers specifically discovered multiple vulnerabilities in Azure Sphere that were patched this month. For more on those specifically, check out the full Vulnerability Spotlight.
## Upcoming public engagements with Talos
Title: Snort 3 and
Talos
Threat Source Newsletter (April 15, 2021)
blogs_talos·2021-04-15
Threat Source Newsletter (April 15, 2021)
## Threat Source Newsletter (April 15, 2021)
Newsletter compiled by Jon Munshaw.
Good afternoon, Talos readers.
If you missed our webinar last week, we've got you covered. We've uploaded an extended version to our YouTube page that includes the scripts used in the presentation. This video will show you how to reverse-engineer and detect Android malware .
We also had Patch Tuesday this week , which featured some more vulnerabilities in Microsoft Exchange Server. Here is a full breakdown of the issues you should know about and Snort rules to keep users protected from exploitation. Cisco Talos researchers specifically discovered multiple vulnerabilities in Azure Sphere that were patched this month. For more on those specifically, check out the full Vulnerability Spotlight .
## Upcoming p
Qualys
April 2021 Patch Tuesday – 108 Vulnerabilities, 19 Critical, Adobe
blogs_qualys·2021-04-14·CVSS 7.8
CVE-2021-28310 [HIGH] April 2021 Patch Tuesday – 108 Vulnerabilities, 19 Critical, Adobe
This month’s Microsoft Patch Tuesday addresses 108 vulnerabilities, of which 19 are rated critical severity and 88 are rated high severity. Adobe released patches for its Photoshop, Digital Editions, and Bridge products.
## CVE-2021-28310: Win32k Elevation of Privilege Vulnerability
Microsoft released patches addressing another 0-day vulnerability (CVE-2021-28310). CVE-2021-28310 is an out-of-bounds (OOB) write vulnerability in dwmcore.dll, which is part of Desktop Window Manager (dwm.exe). There is a public exploit available which is being used in the wild. BITTER APT group is suspected of exploiting this CVE in the wild. This CVE has a temporal score of 7.2 from the vendor and should be prioritized for patching.
## Microsoft Exchange Server Remote Code Execution (RCE) Vulnerabilities
Qualys
April 2021 Patch Tuesday – 108 Vulnerabilities, 19 Critical, Adobe | Qualys
blogs_qualys·2021-04-14·CVSS 7.8
CVE-2021-28310 [HIGH] April 2021 Patch Tuesday – 108 Vulnerabilities, 19 Critical, Adobe | Qualys
This month’s Microsoft Patch Tuesday addresses 108 vulnerabilities, of which 19 are rated critical severity and 88 are rated high severity. Adobe released patches for its Photoshop, Digital Editions, and Bridge products.
#### CVE-2021-28310: Win32k Elevation of Privilege Vulnerability
Microsoft released patches addressing another 0-day vulnerability (CVE-2021-28310). CVE-2021-28310 is an out-of-bounds (OOB) write vulnerability in dwmcore.dll, which is part of Desktop Window Manager (dwm.exe). There is a public exploit available which is being used in the wild. BITTER APT group is suspected of exploiting this CVE in the wild. This CVE has a temporal score of 7.2 from the vendor and should be prioritized for patching.
#### Microsoft Exchange Server Remote Code Execution (RCE) Vulnerabilit
Talos
Microsoft Patch Tuesday for April 2021 — Snort rules and prominent vulnerabilities
blogs_talos·2021-04-13·CVSS 7.8
[HIGH] Microsoft Patch Tuesday for April 2021 — Snort rules and prominent vulnerabilities
## Microsoft Patch Tuesday for April 2021 — Snort rules and prominent vulnerabilities
By Jon Munshaw, with contributions from Vanja Svajcer.
Microsoft released its monthly security update Tuesday, disclosing 108 vulnerabilities across its suite of products, the most in any month so far this year.
Four new remote code execution vulnerabilities in Microsoft Exchange Server are included in today's security update. Microsoft disclosed multiple zero-day vulnerabilities in Exchange Server earlier this year that attackers were exploiting in the wild. Talos encourages everyone with an affected product to update as soon as possible if they have not already and put other mitigation strategies into place in the meantime. Users can also detect the exploitation of the previously disclosed vulnerabil
Trendmicro
April Patch Tuesday Sets Record High for 2021
blogs_trendmicro·2021-04-13·CVSS 7.8
[HIGH] April Patch Tuesday Sets Record High for 2021
## April Patch Tuesday Sets Record High for 2021
April’s Patch Tuesday fixes 114 vulnerabilities in various Microsoft products, a slight increase from March’s 89. This is the most vulnerabilities fixed in a month for 2021 to date, as well as a slight increase from the same month last year.
By: Trend Micro Apr 13, 2021 Read time: ( words)
Save to Folio
April’s Patch Tuesday fixes 114 vulnerabilities in various Microsoft products, a slight increase from March’s 89. This is the most vulnerabilities fixed in a month for 2021 to date, as well as a slight increase from the same month last year.
Of these vulnerabilities, a total of 19 were classified as Critical by Microsoft. Four of these vulnerabilities were already publicly known, with a separate vulnerability already being exploited in t
Trendmicro
April Patch Tuesday Sets Record High for 2021
blogs_trendmicro·2021-04-13·CVSS 7.8
[HIGH] April Patch Tuesday Sets Record High for 2021
# April Patch Tuesday Sets Record High for 2021
April’s Patch Tuesday fixes 114 vulnerabilities in various Microsoft products, a slight increase from March’s 89. This is the most vulnerabilities fixed in a month for 2021 to date, as well as a slight increase from the same month last year.
By: Trend Micro
2021/04/13
Read time: ( words)
Save to Folio
April’s Patch Tuesday fixes 114 vulnerabilities in various Microsoft products, a slight increase from March’s 89. This is the most vulnerabilities fixed in a month for 2021 to date, as well as a slight increase from the same month last year.
Of these vulnerabilities, a total of 19 were classified as Critical by Microsoft. Four of these vulnerabilities were already publicly known, with a separate vulnerability already being exploited in the
Trendmicro
April Patch Tuesday Sets Record High for 2021
blogs_trendmicro·2021-04-13·CVSS 7.8
[HIGH] April Patch Tuesday Sets Record High for 2021
## April Patch Tuesday Sets Record High for 2021
April’s Patch Tuesday fixes 114 vulnerabilities in various Microsoft products, a slight increase from March’s 89. This is the most vulnerabilities fixed in a month for 2021 to date, as well as a slight increase from the same month last year.
By: Trend Micro 2021/04/13 Read time: ( words)
Save to Folio
April’s Patch Tuesday fixes 114 vulnerabilities in various Microsoft products, a slight increase from March’s 89. This is the most vulnerabilities fixed in a month for 2021 to date, as well as a slight increase from the same month last year.
Of these vulnerabilities, a total of 19 were classified as Critical by Microsoft. Four of these vulnerabilities were already publicly known, with a separate vulnerability already being exploited in the
Krebs
Microsoft Patch Tuesday, April 2021 Edition
blogs_krebs·2021-04-13·CVSS 7.8
[HIGH] Microsoft Patch Tuesday, April 2021 Edition
Microsoft today released updates to plug at least 110 security holes in its Windows operating systems and other products. The patches include four security fixes for Microsoft Exchange Server — the same systems that have been besieged by attacks on four separate (and zero-day) bugs in the email software over the past month. Redmond also patched a Windows flaw that is actively being exploited in the wild.
Nineteen of the vulnerabilities fixed this month earned Microsoft’s most-dire “Critical” label, meaning they could be used by malware or malcontents to seize remote control over vulnerable Windows systems without any help from users.
Microsoft released updates to fix four more flaws in Exchange Server versions 2013-2019 ( CVE-2021-28480 , CVE-2021-28481 , CVE-2021-28482 , CVE-2021-28483
Talos
Microsoft Patch Tuesday for April 2021 — Snort rules and prominent vulnerabilities
blogs_talos·2021-04-13·CVSS 7.8
[HIGH] Microsoft Patch Tuesday for April 2021 — Snort rules and prominent vulnerabilities
By Jon Munshaw, with contributions from Vanja Svajcer.
Microsoft released its monthly security update Tuesday, disclosing 108 vulnerabilities across its suite of products, the most in any month so far this year.
Four new remote code execution vulnerabilities in Microsoft Exchange Server are included in today's security update. Microsoft disclosed multiple zero-day vulnerabilities in Exchange Server earlier this year that attackers were exploiting in the wild. Talos encourages everyone with an affected product to update as soon as possible if they have not already and put other mitigation strategies into place in the meantime. Users can also detect the exploitation of the previously disclosed vulnerabilities with Cisco Secure IPS.
The new vulnerabilities Microsoft disclosed today are ide
Tenable
Microsoft’s April 2021 Patch Tuesday Addresses 108 CVEs (CVE-2021-28310)
blogs_tenable·2021-04-13·CVSS 7.8
[HIGH] Microsoft’s April 2021 Patch Tuesday Addresses 108 CVEs (CVE-2021-28310)
## Cloud Exposure
Tenable Cloud Security (CNAPP) Request a demo
Tenable Cloud Vulnerability Management Request a demo
Tenable CIEM Request a demo
Secure your cloud
## Vulnerability Exposure
Tenable Vulnerability Management Try for free
Tenable Security Center Request a demo
Tenable Web App Scanning Try for free
Tenable Patch Management Request a demo
Tenable Enclave Security Request a demo
Tenable Attack Surface Management Request a demo
Tenable Nessus Try for free
## AI Exposure
Tenable AI Exposure Request a demo
## OT/IoT Exposure
Tenable OT Security Request a demo
## Identity Exposure
Tenable Identity Exposure Request a demo
## Business needs
Active Directory
AI Security Posture Management (AI-SPM)
AWS security
Azure security
Cloud Security Posture Man
Krebs
Microsoft Patch Tuesday, April 2021 Edition
blogs_krebs·2021-04-13·CVSS 7.8
[HIGH] Microsoft Patch Tuesday, April 2021 Edition
Microsoft today released updates to plug at least 110 security holes in its Windows operating systems and other products. The patches include four security fixes for Microsoft Exchange Server — the same systems that have been besieged by attacks on four separate (and zero-day) bugs in the email software over the past month. Redmond also patched a Windows flaw that is actively being exploited in the wild.
Nineteen of the vulnerabilities fixed this month earned Microsoft’s most-dire “Critical” label, meaning they could be used by malware or malcontents to seize remote control over vulnerable Windows systems without any help from users.
Microsoft released updates to fix four more flaws in Exchange Server versions 2013-2019 (CVE-2021-28480, CVE-2021-28481, CVE-2021-28482, CVE-2021-28483). In
Tenable
CVE-2021-28480, CVE-2021-28481, CVE-2021-28482, CVE-2021-28483: Four Critical Microsoft Exchange Server Vulnerabilities Patched in April Patch Tuesday
blogs_tenable·2021-04-13·CVSS 9.8
[CRITICAL] CVE-2021-28480, CVE-2021-28481, CVE-2021-28482, CVE-2021-28483: Four Critical Microsoft Exchange Server Vulnerabilities Patched in April Patch Tuesday
## Cloud Exposure
Tenable Cloud Security (CNAPP) Request a demo
Tenable Cloud Vulnerability Management Request a demo
Tenable CIEM Request a demo
Secure your cloud
## Vulnerability Exposure
Tenable Vulnerability Management Try for free
Tenable Security Center Request a demo
Tenable Web App Scanning Try for free
Tenable Patch Management Request a demo
Tenable Enclave Security Request a demo
Tenable Attack Surface Management Request a demo
Tenable Nessus Try for free
## AI Exposure
Tenable AI Exposure Request a demo
## OT/IoT Exposure
Tenable OT Security Request a demo
## Identity Exposure
Tenable Identity Exposure Request a demo
## Business needs
Active Directory
AI Security Posture Management (AI-SPM)
AWS security
Azure security
Cloud Security Posture Man
Crowdstrike
2021 April Patch Tuesday: Updates and Analysis
blogs_crowdstrike·CVSS 7.5
CVE-2026-20929 [HIGH] 2021 April Patch Tuesday: Updates and Analysis
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Video Highlights the 4 Key Steps to Successful Incident Response Dec 02, 2019
Helping Non-Security Stakeholders Understand ATT&CK in 10 Minutes or Less [VI
Crowdstrike
2021 April Patch Tuesday: Updates and Analysis
blogs_crowdstrike·CVSS 7.5
CVE-2026-20929 [HIGH] 2021 April Patch Tuesday: Updates and Analysis
How CrowdStrike is Accelerating Exposure Evaluation as Adversaries Gain Speed Apr 06, 2026
STARDUST CHOLLIMA Likely Compromises Axios npm Package Apr 01, 2026
Falcon for IT Supports Windows Secure Boot Certificate Lifecycle Management Apr 01, 2026
Detecting CVE-2026-20929: Kerberos Authentication Relay via CNAME Abuse Mar 31, 2026
How CrowdStrike is Accelerating Exposure Evaluation as Adversaries Gain Speed Apr 06, 2026
STARDUST CHOLLIMA Likely Compromises Axios npm Package Apr 01, 2026
Falcon for IT Supports Windows Secure Boot Certificate Lifecycle Management Apr 01, 2026
Detecting CVE-2026-20929: Kerberos Authentication Relay via CNAME Abuse Mar 31, 2026
Video Highlights the 4 Key Steps to Successful Incident Response Dec 02, 2019
Helping Non-Security Stakeholders Understand AT
2021-04-13
Published