Security readout for executives and security teams
Plain-English summary
This is a Microsoft Windows information disclosure issue in the Windows Overlay Filter. It requires local, low-privileged access, so it is not a direct internet remote compromise. The business risk is exposure of sensitive information on affected Windows client and server systems if they remain unpatched.
Executive priority
Handle through normal monthly patch governance, with faster action for affected servers or high-sensitivity endpoints. There is no source-backed active exploitation signal in the bundle, but unpatched systems retain a meaningful confidentiality exposure.
Technical view
CVE-2021-26417 is rated CVSS 5.5 with local attack vector, low complexity, low privileges required, no user interaction, unchanged scope, and high confidentiality impact only. The provided sources do not describe the exact data exposed or root cause beyond Windows Overlay Filter information disclosure.
Likely exposure
Exposure is limited to listed Microsoft Windows 10 releases 1809, 1909, 2004, 20H2 and Windows Server 2019, 1909, 2004, 20H2 variants, including Server Core entries. Systems outside those listed are not established as affected by the provided bundle.
Exploitation context
The bundle does not show CISA KEV listing or cited evidence of active exploitation. Exploitation requires local access with low privileges and no user interaction. Treat it as a confidentiality risk that may matter more on shared servers, sensitive workstations, and systems processing regulated data.
Researcher notes
The source data is sparse: no CWE, no detailed root cause, no exploit technique, and no specific leaked information are provided. The CVSS vector supports local, low-privilege information disclosure with high confidentiality impact and official remediation available.
Mitigation direction
- Apply Microsoft security updates referenced by the MSRC advisory.
- Prioritize affected servers and shared Windows endpoints handling sensitive data.
- Check vendor guidance if patch status is unclear for a specific build.
- Reduce unnecessary local user access on affected systems.
Validation and detection
- Inventory Windows versions against the affected product list.
- Confirm April 2021 or later relevant Microsoft security updates are installed.
- Review vulnerability scanner findings for CVE-2021-26417 on Windows assets.
- Validate exceptions with Microsoft advisory data before accepting risk.
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-2021-26417 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
- 5.5 (3.1)
- Known Exploited
- No
- Published
Vector: CVSS:3.1/AV:L/AC:L/PR:L/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:L/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N/E:U/RL:O/RC:C1.83.6Primary CVE scoreVulnerability scoring details
Base CVSS 3.1 score
5.5MediumVector: CVSS:3.1/AV:L/AC:L/PR:L/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-2021-26417CVE 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.