Security readout for executives and security teams
Plain-English summary
CVE-2021-31976 is a Microsoft Server for NFS information disclosure vulnerability. A remote, unauthenticated attacker could potentially read sensitive information from affected Windows systems. The sources rate it high severity because confidentiality impact is high, while integrity and availability are not indicated as affected.
Executive priority
Prioritize remediation for Windows servers exposing NFS, especially where sensitive data is reachable across networks. The issue is high severity but limited to confidentiality in the provided scoring, with no provided evidence of active exploitation.
Technical view
The CVSS 3.1 vector is AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N, indicating network reachability, low complexity, no privileges, and no user interaction. Microsoft lists official remediation availability. The provided sources do not describe root cause details, exploit mechanics, or specific exposed data types.
Likely exposure
Exposure is most relevant to affected Windows client and server versions that run or expose Microsoft Server for NFS. The source bundle lists Windows 8.1, Windows 10 versions, Windows Server 2012/2012 R2, 2016, 2019, and Server Core variants. Confirm actual NFS role usage before assuming reachability.
Exploitation context
The bundle does not show CISA KEV listing or cited evidence of active exploitation. The CVSS exploit maturity is marked unproven. Treat this as a remotely reachable confidentiality risk, but do not claim observed exploitation from the provided evidence.
Researcher notes
Available public detail is sparse. The strongest source-grounded facts are the Microsoft product list, high CVSS score, network unauthenticated attack characteristics, confidentiality-only impact, and official remediation availability. Avoid inferring exploit primitives or affected data classes without additional vendor detail.
Mitigation direction
- Review the MSRC advisory for the correct update per Windows version.
- Apply Microsoft security updates for CVE-2021-31976 through standard patch management.
- Prioritize internet-facing or untrusted-network Server for NFS hosts.
- Restrict NFS exposure to trusted networks until updated.
- Retire or isolate unsupported affected Windows versions where updates are unavailable.
Validation and detection
- Inventory Windows systems in the affected versions listed by Microsoft.
- Identify hosts with Server for NFS installed, enabled, or reachable.
- Confirm the relevant Microsoft security update is installed.
- Review network exposure for NFS services on affected hosts.
- Document exceptions and compensating controls for systems not patched.
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.
CVE-2021-31976 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
- 7.5 (3.1)
- Known Exploited
- No
- Published
Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/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:N/S:U/C:H/I:N/A:N/E:U/RL:O/RC:C3.93.6Primary CVE scoreVulnerability scoring details
Base CVSS 3.1 score
7.5HighVector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/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-2021-31976CVE 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.