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CVE-2021-26855 CISA KEV · Actively exploitedLinked to ransomwareSuited to automated attack · CISA

Microsoft Exchange Server Remote Code Execution Vulnerability

CVSS score

9.1

EPSS probability

%100.0

Risk score

18.2

Published

5 y ago

OverviewPublic Exploits (4)NewsroomVulnerability Timeline
Official patch verified

Etkilenen ürün ve sürüm için yayımlanan güvenlik güncellemesini uygulayın.

Impact on My Inventory

Only the personal products you have added to your account are assessed; an organisation's inventory does not appear here.

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Vulnerability description

DayBreach CVE AI Research

CVE-2021-26855 has vendor, distribution, patch and security-source records on file. We can compare them and prepare an explanation linked to the evidence.

Microsoft Exchange Server Remote Code Execution Vulnerability

IMPACT: Affected Products and Software

Affected Products

The following products are affected by CVE-2021-26855 vulnerability. Where our threat engine knows the exact affected versions, they are listed below.

IDVENDORPRODUCTACTION
1microsoftMicrosoft Exchange Server 2013 Cumulative Update 21 View
2microsoftMicrosoft Exchange Server 2013 Cumulative Update 22 View
3microsoftMicrosoft Exchange Server 2013 Cumulative Update 23 View
4microsoftMicrosoft Exchange Server 2016 Cumulative Update 10 View
5microsoftMicrosoft Exchange Server 2016 Cumulative Update 11 View
6microsoftMicrosoft Exchange Server 2016 Cumulative Update 12 View
7microsoftMicrosoft Exchange Server 2016 Cumulative Update 13 View
8microsoftMicrosoft Exchange Server 2016 Cumulative Update 14 View
9microsoftMicrosoft Exchange Server 2016 Cumulative Update 15 View
10microsoftMicrosoft Exchange Server 2016 Cumulative Update 16 View
11microsoftMicrosoft Exchange Server 2016 Cumulative Update 17 View
12microsoftMicrosoft Exchange Server 2016 Cumulative Update 18 View
13microsoftMicrosoft Exchange Server 2016 Cumulative Update 19 View
14microsoftMicrosoft Exchange Server 2016 Cumulative Update 8 View
15microsoftMicrosoft Exchange Server 2016 Cumulative Update 9 View
16microsoftMicrosoft Exchange Server 2019 View
17microsoftMicrosoft Exchange Server 2019 Cumulative Update 1 View
18microsoftMicrosoft Exchange Server 2019 Cumulative Update 2 View
19microsoftMicrosoft Exchange Server 2019 Cumulative Update 3 View
20microsoftMicrosoft Exchange Server 2019 Cumulative Update 4 View
21microsoftMicrosoft Exchange Server 2019 Cumulative Update 5 View
22microsoftMicrosoft Exchange Server 2019 Cumulative Update 6 View
23microsoftMicrosoft Exchange Server 2019 Cumulative Update 7 View
24microsoftMicrosoft Exchange Server 2019 Cumulative Update 8 View
25microsoftexchange server View
26microsoftexchange server View
27microsoftexchange server View
Total affected vendors: 1|Products: 27

RED HAT CSAF/VEX: Product Impact Check

Red Hat has not yet published a CSAF/VEX impact record for this CVE. This does not mean “not affected”.

SCORING: CVSS from Multiple Sources

CVSS Scores

The Common Vulnerability Scoring System is a standardised framework for assessing the severity of vulnerabilities in software and systems. We collect and display CVSS scores from several sources for each CVE.

SCOREVERSIONSEVERITYVECTORSOURCE
9.8CVSS V31CRITICALCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:HNVD
9.1CVSS V3_1CRITICALCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N/E:F/RL:O/RC:CCVE CNA
9.1CVSS V31CRITICALCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:NNVD
7.5CVSS V2—AV:N/AC:L/Au:N/C:P/I:P/A:PNVD

Patch and Remediation Guide

Solution & Remediation Advisory

Patch verified

5 doğrulanmış yama veya düzeltilmiş sürüm kanıtı bulundu.

cvelist

Microsoft Exchange Server Remote Code Execution Vulnerability

Open source
nvd

NVD tarafından Patch olarak etiketlenmiş referans

Open source
nvd

NVD tarafından Patch olarak etiketlenmiş referans

Open source
reference

Microsoft Exchange Server Remote Code Execution Vulnerability

Open source
reference

Yama veya çözüm referansı

Open source
canonical

Apply updates per vendor instructions.

Confirm the affected product and version against the source evidence above.
Restrict access to internet-facing services and apply network segmentation.
Apply the official update named in the evidence only to the matching product and version.
Monitor server logs and network endpoints for signs of anomalous execution.

Public exploit and active exploitation status

Verified exploit intelligence

CVE-2021-26855 : the database holds 4 public PoC/exploit sources for it. For direct links to the sources, open the Public Exploits tab.

Weakness Classification and Attack Patterns (CWE & CAPEC)

CWE - Common Weakness Enumeration

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

CWE-918: Server-Side Request Forgery (SSRF)

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.

CAPEC-66: SQL InjectionCAPEC-126: Path TraversalCAPEC-28: OS Command Injection

Attack Vector and Accessibility

ExposureAğ üzerinden
PermissionsGerekmiyor
UserGerekmiyor

Official Sources and Advisories

Microsoft Exchange Server Remote Code Execution Vulnerabilitypatchhttps://portal.msrc.microsoft.com/en-US/security-guidance/advisory/CVE-2021-26855patchhttps://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2021-26855nvdCISA Known Exploited Vulnerabilities Catalogkev

CVSS Vector Radar Chart

9.1 / 10
Attack VectorNetworkComplexityLowPrivilegesNoneUser Interact.NoneConfidentialityLowIntegrityNoneAvailabilityNone

Vulnerability Scoring Details

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N/E:F/RL:O/RC:C
Attack VectorNetwork
Attack ComplexityLow
Privileges RequiredNone required
User InteractionNone required
Confidentiality (Gizlilik)Low
Integrity (Bütünlük)None
Availability (Erişilebilirlik)None

Yama doğrulandı

5 doğrulanmış yama veya düzeltilmiş sürüm kanıtı bulundu.

Follow the vendor

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Weakness Type (CWE & CAPEC)

CWE-918

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