Security readout for executives and security teams
Plain-English summary
CVE-2021-1699 is a Windows modem.sys information disclosure issue. An attacker would need local, low-privileged access, so it is less urgent than a remote code execution flaw, but it can expose sensitive information and may assist follow-on compromise.
Executive priority
Treat as a normal patch-cycle vulnerability unless affected high-value systems remain unpatched. It is not described as remotely exploitable or actively exploited, but information disclosure can increase attacker leverage after initial access.
Technical view
The CVSS 3.1 vector is AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N, scoring 5.5. The flaw is local, requires low privileges, needs no user interaction, and impacts confidentiality only. Microsoft lists official remediation availability through its advisory.
Likely exposure
Exposure is limited to listed Microsoft Windows client and server versions, including Windows 7, 8.1, Windows 10 releases, and Windows Server 2008 through 2019/20H2 variants. Systems already updated per Microsoft guidance are likely not exposed.
Exploitation context
The source bundle does not show CISA KEV listing or cited evidence of active exploitation. The vulnerability is local-only, so practical abuse requires prior foothold or authorized low-privileged access on an affected Windows host.
Researcher notes
The bundle provides limited root-cause detail beyond modem.sys information disclosure. Some affected CPE entries appear duplicated or inconsistent, so use Microsoft’s advisory as the authoritative source for exact product/update mapping.
Mitigation direction
- Apply Microsoft security updates addressing CVE-2021-1699.
- Prioritize servers and shared workstations running affected Windows versions.
- Check Microsoft guidance for product-specific update applicability.
- Reduce unnecessary local account access on affected systems.
- Plan replacement or isolation for unsupported Windows versions.
Validation and detection
- Inventory Windows versions against the affected product list.
- Confirm installed updates satisfy Microsoft CVE-2021-1699 guidance.
- Review vulnerability scanner findings for affected CPE matches.
- Validate high-value Windows servers before lower-risk endpoints.
- Track exceptions where patching is delayed.
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-2021-1699 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
- Windows (modem.sys) Information Disclosure VulnerabilityCVE reference · vendor-advisory
- https://portal.msrc.microsoft.com/en-US/security-guidance/advisory/CVE-2021-1699CVE reference · x_refsource_MISC, x_transferred
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.