Security readout for executives and security teams
Plain-English summary
CVE-2021-33739 is a Microsoft Windows Desktop Window Manager Core Library elevation-of-privilege flaw. It requires local access, but no prior privileges or user interaction per the CVSS vector. CISA lists it as known exploited, so unpatched affected Windows systems should be treated as urgent internal-risk exposure.
Executive priority
High priority. Because CISA lists this CVE as known exploited and the impact is full system compromise after local execution, patch affected Windows assets promptly, starting with servers, privileged-user workstations, and internet-adjacent management hosts.
Technical view
The vulnerability affects listed Windows 10 and Windows Server releases and is scored CVSS 8.4 high. The vector is local, low complexity, no privileges, no user interaction, unchanged scope, with high confidentiality, integrity, and availability impact. Microsoft identifies it as an elevation-of-privilege issue in DWM Core Library.
Likely exposure
Exposure is likely where Windows 10 1909, 2004, 20H2, 21H1, Windows Server 2004, or Windows Server 20H2 remain unpatched. The supplied CPE list has some version-label inconsistencies, so validate against Microsoft’s advisory and asset inventory.
Exploitation context
Active exploitation is supported by CISA KEV inclusion. Public sources supplied do not describe exploit mechanics, campaigns, or required local foothold details. Treat this as a likely post-compromise privilege escalation risk rather than a remote initial-access issue.
Researcher notes
No CWE or exploit detail is provided in the source bundle. The CVSS vector indicates local attack surface and no required privileges. Research should focus on build-level exposure, patch verification, and whether affected hosts have suspicious local execution preceding privilege changes.
Mitigation direction
- Apply Microsoft security updates for CVE-2021-33739 through normal Windows patching channels.
- Prioritize systems matching the affected Windows client and server versions.
- Review Microsoft’s advisory for exact fixed builds and deployment notes.
- Retire or isolate unsupported affected builds that cannot receive updates.
- Monitor CISA KEV remediation expectations for externally governed environments.
Validation and detection
- Inventory Windows build numbers across endpoints and servers.
- Compare installed builds against Microsoft’s CVE-2021-33739 advisory.
- Confirm June 2021 or later applicable security updates are installed.
- Check vulnerability scanner results for CVE-2021-33739 specifically.
- Review EDR telemetry for unusual local privilege escalation activity.
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-2021-33739 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
- 8.4 (3.1)
- Known Exploited
- Yes
- Published
Vector: CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H/E:F/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.
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:L/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H/E:F/RL:O/RC:C2.55.9Primary CVE scoreVulnerability scoring details
Base CVSS 3.1 score
8.4HighVector: CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H/E:F/RL:O/RC:C
Source materials
- CVE List V5 sourceCVE List V5
- https://portal.msrc.microsoft.com/en-US/security-guidance/advisory/CVE-2021-33739CVE reference · x_refsource_MISC
- https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2021-33739CVE 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.