Security readout for executives and security teams
This is a remote code execution flaw in Microsoft Exchange Server. An attacker with low-level privileges could run code on an affected server without user interaction. Because Exchange often handles sensitive mail and authentication flows, compromise can create serious business impact. CISA lists this CVE as known exploited, so treat exposure as urgent. Organizations running on-premises Microsoft Exchange Server 2016 CU21 or CU22, or Exchange Server 2019 CU10 or CU11, should assume potential exposure until patch status is verified. The source bundle does not identify Exchange Online or other products as affected. Prioritize this as an urgent Exchange remediation item. The vulnerability affects business-critical email infrastructure, has high impact, and is listed by CISA as known exploited. Delay increases risk of server compromise and downstream mailbox or domain-impacting activity. Mitigation focus: Apply Microsoft security updates or vendor guidance for CVE-2021-42321.; Prioritize remediation for any internet-accessible affected Exchange servers.; Inventory Exchange Server versions and cumulative update levels..
Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.
Conservative CVE-to-ATT&CK context
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ATT&CK lookup starting points
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Execution behavior lookup
The CVE wording references code or command execution, so execution technique review may help defensive triage. This is a Glexia inferred lookup path, not an official MITRE, ATT&CK, or CVE Program mapping.
Open ATT&CK lookupCVE-2021-42321 mapping review
Open the CVE-to-ATT&CK bridge for reviewed, inferred, or future official mappings tied to this CVE.
Open ATT&CK lookup- Severity
- High
- CVSS
- 8.8 (3.1)
- Known Exploited
- Yes
- Published
Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H/E:U/RL:O/RC:C
CNA and ADP enrichment extracted from CVE v5
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CISA KEV status
CVSS vector scores
1 official scoreWe collect every scored CVSS vector available in the official CNA and ADP containers. When more than one version is present, the table keeps the source vectors side by side instead of collapsing them into the highest score.
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H/E:U/RL:O/RC:C2.85.9Primary CVE scoreVulnerability scoring details
Base CVSS 3.1 score
8.8HighVector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H/E:U/RL:O/RC:C
Source materials
- CVE List V5 sourceCVE List V5
- https://portal.msrc.microsoft.com/en-US/security-guidance/advisory/CVE-2021-42321CVE reference · x_refsource_MISC
- https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2021-42321CVE reference · government-resource
Products and packages named in the record
CWE details
CWE links open Glexia weakness intelligence pages with official CWE context, developer remediation guidance, and related CVE mappings.