Exploitation status
CISA KEV · exploited in the wild
Added 2021-11-03.
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Indicator investigation
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Indicator
Type cve · source CISA KEV
ACTIVELY EXPLOITED (CISA KEV)
Vulnerability investigation
CISA confirms this vulnerability has been exploited in the wild. CISA also records known ransomware campaign use. NVD rates the technical severity critical at CVSS 9.1. These are public vulnerability signals, not proof that a specific environment runs an affected version.
Exploitation status
CISA KEV · exploited in the wild
Added 2021-11-03.
30-day exploitation likelihood
Unavailable
FIRST EPSS did not return a score.
Technical severity
9.1 · critical
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N
Affected surface
4 parsed products
Exchange Server, Microsoft Exchange Server 2013, Microsoft Exchange Server 2016
Weakness class
CWE-918: Server-Side Request Forgery (SSRF)
CWE describes the weakness category, not whether a deployed product is reachable or exploitable.
Corpus evidence
2 connectors · 1020 citations
1 related report mention.
Findings stay bounded to named sources and observable infrastructure.
CVE-2021-26855 · CWE context (CWE-918)
The base CVE appears first. Independent evidence is added without blocking the page.
Investigation status
Checking for newly completed evidence
NIST NVD
NVD evidence is available in this response
CISA KEV
Listed in the local CISA KEV catalog
FIRST EPSS
Forensia does not request or publish EPSS while source rights are under review
Reports
Report links are still being resolved
Relationships
Product and vulnerability relationships are still being prepared
Local EPSS row, KEV flag, and catalog notes from stored metadata only.
Apply updates per vendor instructions.
The catalog due date governs U.S. federal civilian agencies; use the action as authoritative remediation guidance, not a universal legal deadline.
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Network · Low · None
NIST NVD CVSS
CVSS measures technical severity and prerequisites; it does not measure observed exploitation likelihood.
Exchange Server, Microsoft Exchange Server 2013, Microsoft Exchange Server 2016, Microsoft Exchange Server 2019
NVD CPE / CISA product metadata
Product names are candidate applicability pivots. Confirm exact deployed versions and vendor ranges before remediation decisions.
The CVE appears in locally ingested reporting, providing public context beyond the scoring feeds.
Forensia report text match
A text mention does not by itself confirm exploitation, affected versions, or campaign attribution.