Security readout for executives and security teams
Plain-English summary
CVE-2021-1655 is a Microsoft Windows CSC Service privilege escalation flaw. An attacker who already has low-level local access could potentially gain high-impact control over confidentiality, integrity, and availability. It is important, but not a remote internet-entry vulnerability based on the provided CVSS vector.
Executive priority
Prioritize remediation in normal high-severity patch cycles. Escalate for shared workstations, terminal servers, and systems with many local users because successful exploitation could turn limited access into broad system compromise.
Technical view
The source bundle describes a Windows CSC Service Elevation of Privilege vulnerability with CVSS 3.1 score 7.8: local attack vector, low complexity, low privileges required, no user interaction, unchanged scope, and high C/I/A impact. Microsoft is the affected vendor across listed Windows client and server versions.
Likely exposure
Exposure is most likely on unpatched Windows 7, 8.1, 10, Windows Server 2008, 2016, 2019, and listed semiannual server releases. Risk is higher where local users, shared systems, or untrusted code execution are plausible.
Exploitation context
The bundle does not identify active exploitation, and KEV is false. The CVSS exploit code maturity is marked unproven. Treat this as a local post-access escalation risk rather than confirmed in-the-wild activity.
Researcher notes
Public detail in the bundle is sparse: no CWE, no root cause, and no exploit mechanics are provided. The defensible assessment is based on Microsoft advisory metadata, affected products, CVSS vector, and the absence of KEV evidence.
Mitigation direction
- Apply the Microsoft security update or remediation referenced in the MSRC advisory.
- Prioritize systems allowing local interactive access or execution of untrusted code.
- Review unsupported Windows versions for extended security update coverage or retirement.
- Track Microsoft Update Guide changes for any revised remediation guidance.
Validation and detection
- Inventory Windows versions against the affected product list in the source bundle.
- Confirm applicable January 2021 or later Microsoft security updates are installed.
- Check vulnerability management results for CVE-2021-1655 on endpoints and servers.
- Document exceptions for unsupported or extended-support Windows systems.
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-2021-1655 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
- Windows CSC Service Elevation of Privilege VulnerabilityCVE reference · vendor-advisory
- https://portal.msrc.microsoft.com/en-US/security-guidance/advisory/CVE-2021-1655CVE 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.