Security readout for executives and security teams
Plain-English summary
This is a Windows Bluetooth pairing weakness. A nearby attacker could bypass the intended pairing security and potentially impersonate a device during passkey entry. Microsoft rated it high severity and issued an update that rejects a specific unsafe public-key condition during pairing.
Executive priority
Treat as a high-priority endpoint and server patching issue where Bluetooth is present or pairing is used. It is not described as remotely internet-exploitable or actively exploited in the provided sources, so urgency should be driven by asset exposure and patch coverage.
Technical view
CVE-2021-1638 concerns Bluetooth Passkey Entry Protocol impersonation. Microsoft’s update fails pairing attempts when the remote device exchanges a public key with the same X coordinate as the local public key. CVSS 3.1 is 7.7, with local attack vector, no privileges, no user interaction, and high confidentiality and integrity impact.
Likely exposure
Exposure is limited to listed Microsoft Windows 10 and Windows Server versions, including 1803, 1809, 1909, 2004, 20H2, Server 2019, and Server Core variants. Practical risk depends on Bluetooth capability, pairing use, physical or radio proximity, and patch status.
Exploitation context
The bundle does not show CISA KEV listing or cited active exploitation. The attack vector is local, consistent with Bluetooth proximity rather than internet-reachable exploitation. Sources do not provide public exploit details, observed campaigns, or weaponization status.
Researcher notes
Evidence is strongest for Microsoft’s affected-products list, CVSS, and update behavior. The bundle references a Bluetooth SIG statement but does not include its URL or details. No CWE, exploit proof, KEV status, or non-Microsoft affected product data is provided.
Mitigation direction
- Apply Microsoft’s software update for CVE-2021-1638 to affected Windows systems.
- Use MSRC guidance to confirm OS-specific update applicability and replacement status.
- Prioritize assets with Bluetooth hardware, pairing workflows, or high-value local data access.
- Track unsupported Windows versions separately for upgrade or compensating-risk decisions.
Validation and detection
- Inventory Windows versions against the affected product list in the source bundle.
- Confirm CVE-2021-1638 update installation through endpoint patch management records.
- Identify systems with Bluetooth hardware enabled or operational pairing requirements.
- Document exceptions where affected systems cannot be patched immediately.
- Avoid exploit-style validation; rely on patch and configuration evidence.
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-2021-1638 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
- 7.7 (3.1)
- Known Exploited
- No
- Published
Vector: CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:H/I:H/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:N/UI:N/S:U/C:H/I:H/A:N/E:U/RL:O/RC:C2.55.2Primary CVE scoreVulnerability scoring details
Base CVSS 3.1 score
7.7HighVector: CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N/E:U/RL:O/RC:C
Source materials
- CVE List V5 sourceCVE List V5
- Windows Bluetooth Security Feature Bypass VulnerabilityCVE reference · vendor-advisory
- https://portal.msrc.microsoft.com/en-US/security-guidance/advisory/CVE-2021-1638CVE 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.