CVE-2021-26858 (GCVE-0-2021-26858)
Vulnerability from cvelistv5 – Published: 2021-03-02 23:55 – Updated: 2025-10-21 23:25Title
Microsoft Exchange Server Remote Code Execution Vulnerability
Summary
Microsoft Exchange Server Remote Code Execution Vulnerability
Severity
SSVC
Exploitation: active
Automatable: no
Technical Impact: total
CISA Coordinator (v2.0.3)
CWE
- Remote Code Execution
- CWE-noinfo Not enough information
Assigner
References
2 references
| URL | Tags |
|---|---|
| https://portal.msrc.microsoft.com/en-US/security-… | x_refsource_MISC |
| https://www.cisa.gov/known-exploited-vulnerabilit… | government-resource |
Impacted products
24 products
| Vendor | Product | Version | |
|---|---|---|---|
| Microsoft | Microsoft Exchange Server 2019 |
Affected:
15.02.0 , < publication
(custom)
cpe:2.3:a:microsoft:exchange_server:2019:*:*:*:*:*:*:* |
|
| Microsoft | Microsoft Exchange Server 2013 Cumulative Update 22 |
Affected:
15.00.0 , < publication
(custom)
cpe:2.3:a:microsoft:exchange_server:2013:cumulative_update_22:*:*:*:*:*:* |
|
| Microsoft | Microsoft Exchange Server 2019 Cumulative Update 2 |
Affected:
15.02.0 , < publication
(custom)
cpe:2.3:a:microsoft:exchange_server:2019:cumulative_update_2:*:*:*:*:*:* |
|
| Microsoft | Microsoft Exchange Server 2016 Cumulative Update 13 |
Affected:
15.01.0 , < publication
(custom)
cpe:2.3:a:microsoft:exchange_server:2016:cumulative_update_13:*:*:*:*:*:* |
|
| Microsoft | Microsoft Exchange Server 2013 Cumulative Update 23 |
Affected:
15.00.0 , < publication
(custom)
cpe:2.3:a:microsoft:exchange_server:2013:cumulative_update_23:*:*:*:*:*:* |
|
| Microsoft | Microsoft Exchange Server 2019 Cumulative Update 3 |
Affected:
15.02.0 , < publication
(custom)
cpe:2.3:a:microsoft:exchange_server:2019:cumulative_update_3:*:*:*:*:*:* |
|
| Microsoft | Microsoft Exchange Server 2016 Cumulative Update 14 |
Affected:
15.01.0 , < publication
(custom)
cpe:2.3:a:microsoft:exchange_server:2016:cumulative_update_14:*:*:*:*:*:* |
|
| Microsoft | Microsoft Exchange Server 2019 Cumulative Update 4 |
Affected:
15.02.0 , < publication
(custom)
cpe:2.3:a:microsoft:exchange_server:2019:cumulative_update_4:*:*:*:*:*:* |
|
| Microsoft | Microsoft Exchange Server 2016 Cumulative Update 15 |
Affected:
15.01.0 , < publication
(custom)
cpe:2.3:a:microsoft:exchange_server:2016:cumulative_update_15:*:*:*:*:*:* |
|
| Microsoft | Microsoft Exchange Server 2019 Cumulative Update 5 |
Affected:
15.02.0 , < publication
(custom)
cpe:2.3:a:microsoft:exchange_server:2019:cumulative_update_5:*:*:*:*:*:* |
|
| Microsoft | Microsoft Exchange Server 2019 Cumulative Update 6 |
Affected:
15.02.0 , < publication
(custom)
cpe:2.3:a:microsoft:exchange_server:2019:cumulative_update_6:*:*:*:*:*:* |
|
| Microsoft | Microsoft Exchange Server 2016 Cumulative Update 16 |
Affected:
15.01.0 , < publication
(custom)
cpe:2.3:a:microsoft:exchange_server:2016:cumulative_update_16:*:*:*:*:*:* |
|
| Microsoft | Microsoft Exchange Server 2016 Cumulative Update 17 |
Affected:
15.01.0 , < publication
(custom)
cpe:2.3:a:microsoft:exchange_server:2016:cumulative_update_17:*:*:*:*:*:* |
|
| Microsoft | Microsoft Exchange Server 2019 Cumulative Update 7 |
Affected:
15.02.0 , < publication
(custom)
cpe:2.3:a:microsoft:exchange_server:2019:cumulative_update_7:*:*:*:*:*:* |
|
| Microsoft | Microsoft Exchange Server 2016 Cumulative Update 18 |
Affected:
15.01.0 , < publication
(custom)
cpe:2.3:a:microsoft:exchange_server:2016:cumulative_update_18:*:*:*:*:*:* |
|
| Microsoft | Microsoft Exchange Server 2016 Cumulative Update 19 |
Affected:
15.01.0 , < publication
(custom)
cpe:2.3:a:microsoft:exchange_server:2016:cumulative_update_19:*:*:*:*:*:* |
|
| Microsoft | Microsoft Exchange Server 2019 Cumulative Update 8 |
Affected:
15.02.0 , < publication
(custom)
cpe:2.3:a:microsoft:exchange_server:2019:cumulative_update_8:*:*:*:*:*:* |
|
| Microsoft | Microsoft Exchange Server 2013 Cumulative Update 21 |
Affected:
15.00.0 , < publication
(custom)
cpe:2.3:a:microsoft:exchange_server:2013:cumulative_update_21:*:*:*:*:*:* |
|
| Microsoft | Microsoft Exchange Server 2016 Cumulative Update 12 |
Affected:
15.01.0 , < publication
(custom)
cpe:2.3:a:microsoft:exchange_server:2016:cumulative_update_12:*:*:*:*:*:* |
|
| Microsoft | Microsoft Exchange Server 2016 Cumulative Update 8 |
Affected:
15.01.0 , < publication
(custom)
cpe:2.3:a:microsoft:exchange_server:2016:cumulative_update_8:*:*:*:*:*:* |
|
| Microsoft | Microsoft Exchange Server 2019 Cumulative Update 1 |
Affected:
15.02.0 , < publication
(custom)
cpe:2.3:a:microsoft:exchange_server:2019:cumulative_update_1:*:*:*:*:*:* |
|
| Microsoft | Microsoft Exchange Server 2016 Cumulative Update 9 |
Affected:
15.01.0 , < publication
(custom)
cpe:2.3:a:microsoft:exchange_server:2016:cumulative_update_9:*:*:*:*:*:* |
|
| Microsoft | Microsoft Exchange Server 2016 Cumulative Update 10 |
Affected:
15.01.0 , < publication
(custom)
cpe:2.3:a:microsoft:exchange_server:2016:cumulative_update_10:*:*:*:*:*:* |
|
| Microsoft | Microsoft Exchange Server 2016 Cumulative Update 11 |
Affected:
15.01.0 , < publication
(custom)
cpe:2.3:a:microsoft:exchange_server:2016:cumulative_update_11:*:*:*:*:*:* |
Date Public
2021-03-02 08:00
CISA KEV
Known Exploited Vulnerability - GCVE BCP-07 Compliant
KEV entry ID: 1ed4df3d-25d7-4ae8-957e-4847bafa3266
Exploited: Yes
Timestamps
First Seen: 2021-11-03
Asserted: 2021-11-03
Scope
Notes: KEV entry: Microsoft Exchange Server Remote Code Execution Vulnerability | Affected: Microsoft / Exchange Server | 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. | Due date: 2022-05-03 | Known ransomware campaign use (KEV): Known | Notes (KEV): 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-2021-26858
Evidence
Type: Vendor Report
Signal: Successful Exploitation
Confidence: 80%
Source: cisa-kev
Details
| Cwes | |
|---|---|
| Feed | CISA Known Exploited Vulnerabilities Catalog |
| Product | Exchange Server |
| Due Date | 2022-05-03 |
| Date Added | 2021-11-03 |
| Vendorproject | Microsoft |
| Vulnerabilityname | Microsoft Exchange Server Remote Code Execution Vulnerability |
| Knownransomwarecampaignuse | Known |
References
Created: 2026-02-02 12:28 UTC
| Updated: 2026-02-06 07:17 UTC
KEVintel KEV
Known Exploited Vulnerability - GCVE BCP-07 Compliant
KEV entry ID: 24d97951-6f22-4906-936e-87b0a47ba150
Exploited: Yes
Timestamps
First Seen: 2021-11-03
Asserted: 2021-11-03
Scope
Notes: KEVIntel entry: Microsoft Exchange Server Remote Code Execution Vulnerability | Affected: Microsoft / Microsoft Exchange Server 2019, Microsoft Exchange Server 2013 Cumulative Update 22, Microsoft Exchange Server 2019 Cumulative Update 2, Microsoft Exchange Server 2016 Cumulative Update 13, Microsoft Exchange Server 2013 Cumulative Update 23, Microsoft Exchange Server 2019 Cumulative Update 3, Microsoft Exchange Server 2016 Cumulative Update 14, Microsoft Exchange Server 2019 Cumulative Update 4, Microsoft Exchange Server 2016 Cumulative Update 15, Microsoft Exchange Server 2019 Cumulative Update 5, Microsoft Exchange Server 2019 Cumulative Update 6, Microsoft Exchange Server 2016 Cumulative Update 16, Microsoft Exchange Server 2016 Cumulative Update 17, Microsoft Exchange Server 2019 Cumulative Update 7, Microsoft Exchange Server 2016 Cumulative Update 18, Microsoft Exchange Server 2016 Cumulative Update 19, Microsoft Exchange Server 2019 Cumulative Update 8, Microsoft Exchange Server 2013 Cumulative Update 21, Microsoft Exchange Server 2016 Cumulative Update 12, Microsoft Exchange Server 2016 Cumulative Update 8, Microsoft Exchange Server 2019 Cumulative Update 1, Microsoft Exchange Server 2016 Cumulative Update 9, Microsoft Exchange Server 2016 Cumulative Update 10, Microsoft Exchange Server 2016 Cumulative Update 11 | CVSS: 7.8 (HIGH) | EPSS: 0.89509 | Used in malware: yes | Not yet in CISA KEV: False
Evidence
Type: Public Report
Signal: Confirmed Compromise
Confidence: 70%
Source: kevintel
Details
| Feed | KEVIntel (kevintel.com) |
|---|---|
| Title | Microsoft Exchange Server Remote Code Execution Vulnerability |
| Vendor | Microsoft |
| Product | Microsoft Exchange Server 2019, Microsoft Exchange Server 2013 Cumulative Update 22, Microsoft Exchange Server 2019 Cumulative Update 2, Microsoft Exchange Server 2016 Cumulative Update 13, Microsoft Exchange Server 2013 Cumulative Update 23, Microsoft Exchange Server 2019 Cumulative Update 3, Microsoft Exchange Server 2016 Cumulative Update 14, Microsoft Exchange Server 2019 Cumulative Update 4, Microsoft Exchange Server 2016 Cumulative Update 15, Microsoft Exchange Server 2019 Cumulative Update 5, Microsoft Exchange Server 2019 Cumulative Update 6, Microsoft Exchange Server 2016 Cumulative Update 16, Microsoft Exchange Server 2016 Cumulative Update 17, Microsoft Exchange Server 2019 Cumulative Update 7, Microsoft Exchange Server 2016 Cumulative Update 18, Microsoft Exchange Server 2016 Cumulative Update 19, Microsoft Exchange Server 2019 Cumulative Update 8, Microsoft Exchange Server 2013 Cumulative Update 21, Microsoft Exchange Server 2016 Cumulative Update 12, Microsoft Exchange Server 2016 Cumulative Update 8, Microsoft Exchange Server 2019 Cumulative Update 1, Microsoft Exchange Server 2016 Cumulative Update 9, Microsoft Exchange Server 2016 Cumulative Update 10, Microsoft Exchange Server 2016 Cumulative Update 11 |
| Added Date | 2021-11-03T00:00:00.000Z |
| Cvss Score | 7.8 |
| Epss Score | 0.89509 |
| Cvss Severity | HIGH |
| Epss Percentile | 0.99769 |
| Used In Malware | yes |
| Ahead Of Cisa Kev | None |
| Not Yet In Cisa Kev | False |
References
Created: 2026-06-19 12:48 UTC
| Updated: 2026-06-19 12:48 UTC
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"dueDate": "2022-05-03",
"knownRansomwareCampaignUse": "Known",
"notes": "Reference CISA\u0027s 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-2021-26858",
"product": "Exchange Server",
"requiredAction": "Apply updates per vendor instructions.",
"shortDescription": "Microsoft Exchange Server contains an unspecified vulnerability that allows for remote code execution. This vulnerability is part of the ProxyLogon exploit chain.",
"vendorProject": "Microsoft",
"vulnerabilityName": "Microsoft Exchange Server Remote Code Execution Vulnerability"
},
"epss": {
"cve": "CVE-2021-26858",
"date": "2026-06-19",
"epss": "0.89509",
"percentile": "0.99769"
},
"fkie_nvd": {
"cisaActionDue": "2021-04-16",
"cisaExploitAdd": "2021-11-03",
"cisaRequiredAction": "Apply updates per vendor instructions.",
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\"versionType\": \"custom\"}], \"platforms\": [\"x64-based Systems\"]}, {\"cpes\": [\"cpe:2.3:a:microsoft:exchange_server:2019:cumulative_update_5:*:*:*:*:*:*\"], \"vendor\": \"Microsoft\", \"product\": \"Microsoft Exchange Server 2019 Cumulative Update 5\", \"versions\": [{\"status\": \"affected\", \"version\": \"15.02.0\", \"lessThan\": \"publication\", \"versionType\": \"custom\"}], \"platforms\": [\"x64-based Systems\"]}, {\"cpes\": [\"cpe:2.3:a:microsoft:exchange_server:2019:cumulative_update_6:*:*:*:*:*:*\"], \"vendor\": \"Microsoft\", \"product\": \"Microsoft Exchange Server 2019 Cumulative Update 6\", \"versions\": [{\"status\": \"affected\", \"version\": \"15.02.0\", \"lessThan\": \"publication\", \"versionType\": \"custom\"}], \"platforms\": [\"x64-based Systems\"]}, {\"cpes\": [\"cpe:2.3:a:microsoft:exchange_server:2016:cumulative_update_16:*:*:*:*:*:*\"], \"vendor\": \"Microsoft\", \"product\": \"Microsoft Exchange Server 2016 Cumulative Update 16\", \"versions\": [{\"status\": \"affected\", \"version\": \"15.01.0\", \"lessThan\": \"publication\", \"versionType\": \"custom\"}], \"platforms\": [\"x64-based Systems\"]}, {\"cpes\": [\"cpe:2.3:a:microsoft:exchange_server:2016:cumulative_update_17:*:*:*:*:*:*\"], \"vendor\": \"Microsoft\", \"product\": \"Microsoft Exchange Server 2016 Cumulative Update 17\", \"versions\": [{\"status\": \"affected\", \"version\": \"15.01.0\", \"lessThan\": \"publication\", \"versionType\": \"custom\"}], \"platforms\": [\"x64-based Systems\"]}, {\"cpes\": [\"cpe:2.3:a:microsoft:exchange_server:2019:cumulative_update_7:*:*:*:*:*:*\"], \"vendor\": \"Microsoft\", \"product\": \"Microsoft Exchange Server 2019 Cumulative Update 7\", \"versions\": [{\"status\": \"affected\", \"version\": \"15.02.0\", \"lessThan\": \"publication\", \"versionType\": \"custom\"}], \"platforms\": [\"x64-based Systems\"]}, {\"cpes\": [\"cpe:2.3:a:microsoft:exchange_server:2016:cumulative_update_18:*:*:*:*:*:*\"], \"vendor\": \"Microsoft\", \"product\": \"Microsoft Exchange Server 2016 Cumulative Update 18\", \"versions\": [{\"status\": \"affected\", \"version\": \"15.01.0\", \"lessThan\": \"publication\", \"versionType\": \"custom\"}], \"platforms\": [\"x64-based Systems\"]}, {\"cpes\": [\"cpe:2.3:a:microsoft:exchange_server:2016:cumulative_update_19:*:*:*:*:*:*\"], \"vendor\": \"Microsoft\", \"product\": \"Microsoft Exchange Server 2016 Cumulative Update 19\", \"versions\": [{\"status\": \"affected\", \"version\": \"15.01.0\", \"lessThan\": \"publication\", \"versionType\": \"custom\"}], \"platforms\": [\"x64-based Systems\"]}, {\"cpes\": [\"cpe:2.3:a:microsoft:exchange_server:2019:cumulative_update_8:*:*:*:*:*:*\"], \"vendor\": \"Microsoft\", \"product\": \"Microsoft Exchange Server 2019 Cumulative Update 8\", \"versions\": [{\"status\": \"affected\", \"version\": \"15.02.0\", \"lessThan\": \"publication\", \"versionType\": \"custom\"}], \"platforms\": [\"x64-based Systems\"]}, {\"cpes\": [\"cpe:2.3:a:microsoft:exchange_server:2013:cumulative_update_21:*:*:*:*:*:*\"], \"vendor\": \"Microsoft\", \"product\": \"Microsoft Exchange Server 2013 Cumulative Update 21\", \"versions\": [{\"status\": \"affected\", \"version\": \"15.00.0\", \"lessThan\": \"publication\", \"versionType\": \"custom\"}], \"platforms\": [\"x64-based Systems\"]}, {\"cpes\": [\"cpe:2.3:a:microsoft:exchange_server:2016:cumulative_update_12:*:*:*:*:*:*\"], \"vendor\": \"Microsoft\", \"product\": \"Microsoft Exchange Server 2016 Cumulative Update 12\", \"versions\": [{\"status\": \"affected\", \"version\": \"15.01.0\", \"lessThan\": \"publication\", \"versionType\": \"custom\"}], \"platforms\": [\"x64-based Systems\"]}, {\"cpes\": [\"cpe:2.3:a:microsoft:exchange_server:2016:cumulative_update_8:*:*:*:*:*:*\"], \"vendor\": \"Microsoft\", \"product\": \"Microsoft Exchange Server 2016 Cumulative Update 8\", \"versions\": [{\"status\": \"affected\", \"version\": \"15.01.0\", \"lessThan\": \"publication\", \"versionType\": \"custom\"}], \"platforms\": [\"x64-based Systems\"]}, {\"cpes\": [\"cpe:2.3:a:microsoft:exchange_server:2019:cumulative_update_1:*:*:*:*:*:*\"], \"vendor\": \"Microsoft\", \"product\": \"Microsoft Exchange Server 2019 Cumulative Update 1\", \"versions\": [{\"status\": \"affected\", \"version\": \"15.02.0\", \"lessThan\": \"publication\", \"versionType\": \"custom\"}], \"platforms\": [\"x64-based Systems\"]}, {\"cpes\": [\"cpe:2.3:a:microsoft:exchange_server:2016:cumulative_update_9:*:*:*:*:*:*\"], \"vendor\": \"Microsoft\", \"product\": \"Microsoft Exchange Server 2016 Cumulative Update 9\", \"versions\": [{\"status\": \"affected\", \"version\": \"15.01.0\", \"lessThan\": \"publication\", \"versionType\": \"custom\"}], \"platforms\": [\"x64-based Systems\"]}, {\"cpes\": [\"cpe:2.3:a:microsoft:exchange_server:2016:cumulative_update_10:*:*:*:*:*:*\"], \"vendor\": \"Microsoft\", \"product\": \"Microsoft Exchange Server 2016 Cumulative Update 10\", \"versions\": [{\"status\": \"affected\", \"version\": \"15.01.0\", \"lessThan\": \"publication\", \"versionType\": \"custom\"}], \"platforms\": [\"x64-based Systems\"]}, {\"cpes\": [\"cpe:2.3:a:microsoft:exchange_server:2016:cumulative_update_11:*:*:*:*:*:*\"], \"vendor\": \"Microsoft\", \"product\": \"Microsoft Exchange Server 2016 Cumulative Update 11\", \"versions\": [{\"status\": \"affected\", \"version\": \"15.01.0\", \"lessThan\": \"publication\", \"versionType\": \"custom\"}], \"platforms\": [\"x64-based Systems\"]}], \"datePublic\": \"2021-03-02T08:00:00.000Z\", \"references\": [{\"url\": \"https://portal.msrc.microsoft.com/en-US/security-guidance/advisory/CVE-2021-26858\", \"tags\": [\"x_refsource_MISC\"]}], \"descriptions\": [{\"lang\": \"en-US\", \"value\": \"Microsoft Exchange Server Remote Code Execution Vulnerability\"}], \"problemTypes\": [{\"descriptions\": [{\"lang\": \"en-US\", \"type\": \"Impact\", \"description\": \"Remote Code Execution\"}]}], \"providerMetadata\": {\"orgId\": \"f38d906d-7342-40ea-92c1-6c4a2c6478c8\", \"shortName\": \"microsoft\", \"dateUpdated\": \"2023-12-29T20:08:57.719Z\"}}}",
"cveMetadata": "{\"cveId\": \"CVE-2021-26858\", \"state\": \"PUBLISHED\", \"dateUpdated\": \"2025-10-21T23:25:52.837Z\", \"dateReserved\": \"2021-02-08T00:00:00.000Z\", \"assignerOrgId\": \"f38d906d-7342-40ea-92c1-6c4a2c6478c8\", \"datePublished\": \"2021-03-02T23:55:27.000Z\", \"assignerShortName\": \"microsoft\"}",
"dataType": "CVE_RECORD",
"dataVersion": "5.1"
}
}
}
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Experimental. This forecast is provided for visualization only and may change without notice. Do not use it for operational decisions.
Forecast uses a logistic model when the trend is rising, or an exponential decay model when the trend is falling. Fitted via linearized least squares.
Sightings
| Author | Source | Type | Date | Other |
|---|
Nomenclature
- Seen: The vulnerability was mentioned, discussed, or observed by the user.
- Confirmed: The vulnerability has been validated from an analyst's perspective.
- Published Proof of Concept: A public proof of concept is available for this vulnerability.
- Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
- Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
- Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
- Not confirmed: The user expressed doubt about the validity of the vulnerability.
- Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.
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