Security readout for executives and security teams
Plain-English summary
CVE-2021-31195 is a Microsoft Exchange Server vulnerability described as remote code execution. The supplied CVSS data rates it medium, requires user interaction, and shows high confidentiality impact. Organizations running the listed on-premises Exchange cumulative updates should treat it as a priority maintenance issue, especially if mail infrastructure is exposed to untrusted networks.
Executive priority
Schedule remediation in the normal security update cycle, accelerated for internet-facing Exchange systems. This is not supported as actively exploited in the supplied evidence, but Exchange compromise can create material email and identity risk.
Technical view
The affected products are Exchange Server 2013 CU23, 2016 CU19/CU20, and 2019 CU8/CU9. The CVSS 3.1 vector is network-accessible, low complexity, no privileges required, user interaction required, unchanged scope, and high confidentiality impact. CWE-290 is listed, indicating spoofing-related authentication weakness. The bundle provides no exploit mechanics.
Likely exposure
Exposure is limited to the specific Exchange Server cumulative updates listed in the source bundle. Internet-facing or partner-accessible Exchange deployments on those versions are the most relevant assets to review. The bundle does not identify Exchange Online or other Microsoft products as affected.
Exploitation context
The source bundle does not show CISA KEV listing and the CVSS exploit maturity is unproven. Do not assume active exploitation from the provided evidence. The user-interaction requirement lowers immediacy, but Exchange’s business-critical role still raises operational concern.
Researcher notes
There is a notable mismatch between the RCE title and CVSS impacts showing confidentiality only, with user interaction required. Treat the vendor advisory as authoritative for remediation. The bundle lacks exploit details, vulnerable component information, and workaround specifics.
Mitigation direction
- Identify Exchange servers and cumulative update levels across all environments.
- Follow Microsoft’s CVE-2021-31195 advisory for applicable security updates or guidance.
- Prioritize remediation for externally reachable Exchange servers first.
- Restrict unnecessary external access to Exchange services where business operations allow.
- Monitor Microsoft guidance for any later clarification or workaround details.
Validation and detection
- Confirm whether any server runs Exchange 2013 CU23, 2016 CU19/CU20, or 2019 CU8/CU9.
- Check patch records against Microsoft’s CVE-2021-31195 advisory.
- Review perimeter exposure for affected Exchange services.
- Look for compensating controls limiting access to Exchange from untrusted networks.
- Document any systems awaiting vendor-approved remediation.
Public sources used
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
These mappings and lookup hints may be relevant to the vulnerability behavior, CWE, affected product, or exposure path. Glexia-inferred context is not an official MITRE, ATT&CK, CWE, or CVE Program mapping.
ATT&CK lookup starting points
Use these exact CWE pages and searches to review the Glexia ATT&CK library from this CVE's weakness and description context.
CWE-290: Exact CWE lookup
Use the exact CWE identifier as the starting point before reviewing related ATT&CK behavior. Open the exact CWE lookup page first, then review the ATT&CK searches from that MITRE weakness context. This is a Glexia lookup hint, not an official ATT&CK mapping.
Open ATT&CK lookupExecution 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-2021-31195 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
- Medium
- CVSS
- 6.5 (3.1)
- Known Exploited
- No
- Published
Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:N/A:N/E:U/RL:O/RC:C
CNA and ADP enrichment extracted from CVE v5
These fields come from the CVE record and ADP containers, not from Glexia's Take. They preserve time-varying source decisions such as CISA SSVC, KEV status, CVSS metrics, and provider references.
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:N/UI:R/S:U/C:H/I:N/A:N/E:U/RL:O/RC:C2.83.6Primary CVE scoreVulnerability scoring details
Base CVSS 3.1 score
6.5MediumVector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:N/A:N/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-2021-31195CVE reference · x_refsource_MISC
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.
Authentication Bypass by Spoofing
Authentication Bypass by Spoofing represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.