Security readout for executives and security teams
Plain-English summary
This is a Windows local privilege escalation flaw. An attacker who already has low-privileged local access could potentially gain higher privileges on affected Windows systems. The business risk is post-compromise escalation, not initial internet entry.
Executive priority
Treat this as a high-priority endpoint and server hardening issue. It is most urgent where untrusted users, malware, or compromised accounts may gain local access.
Technical view
CVE-2021-42286 affects Microsoft Windows Core Shell SI Host Extension Framework for Composable Shell. CVSS 3.1 is 7.8 with local attack vector, low complexity, low privileges required, no user interaction, and high confidentiality, integrity, and availability impact.
Likely exposure
Exposure is limited to listed affected Windows 10 and Windows Server versions: Windows 10 21H1, 2004, 20H2, and Windows Server 2004/20H2 builds identified in the bundle.
Exploitation context
The source bundle does not show CISA KEV listing or active exploitation evidence. The CVSS vector marks exploit maturity as unproven and remediation level as official fix available.
Researcher notes
Evidence is sparse: no CWE is provided and the public description is generic. Focus validation on affected Windows builds, local privilege boundaries, and Microsoft’s official advisory rather than assuming exploit mechanics.
Mitigation direction
- Apply applicable Microsoft security updates or vendor guidance for CVE-2021-42286.
- Prioritize affected Windows 10 and Windows Server 2004, 20H2, and 21H1 assets.
- Restrict local user access and administrative rights where patching is delayed.
- Monitor Microsoft MSRC for supersedence or platform-specific update guidance.
Validation and detection
- Inventory Windows assets for the affected product versions and build numbers listed in the bundle.
- Check patch compliance against Microsoft guidance for CVE-2021-42286.
- Confirm vulnerability scanner findings map to the affected CPEs and OS builds.
- Review endpoint privilege controls for systems that cannot be patched promptly.
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.
Privilege behavior lookup
The CVE wording references privilege impact, so privilege escalation and authorization behavior review may help. This is a Glexia inferred lookup path, not an official MITRE, ATT&CK, or CVE Program mapping.
Open ATT&CK lookupCVE-2021-42286 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
- 7.8 (3.1)
- Known Exploited
- No
- Published
Vector: CVSS:3.1/AV:L/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
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:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H/E:U/RL:O/RC:C1.85.9Primary CVE scoreVulnerability scoring details
Base CVSS 3.1 score
7.8HighVector: CVSS:3.1/AV:L/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-2021-42286CVE 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.