Security readout for executives and security teams
Plain-English summary
This is a Windows privilege-escalation flaw in Win32k. An attacker who already has low-level local access could gain higher privileges, increasing the impact of phishing, malware, or a compromised user account. CISA KEV listing means defenders should treat it as exploited and not defer remediation.
Executive priority
Treat this as a high-priority patch compliance issue. It is not described as remotely exploitable by itself, but known exploitation and full high-impact outcomes make it important for reducing post-compromise escalation risk.
Technical view
CVE-2021-41357 affects listed Windows 10, Windows 11 21H2, Windows Server 2022, and Windows Server 2004/20H2 builds. CVSS 3.1 is 7.8 with local attack vector, low complexity, low privileges required, no user interaction, and high confidentiality, integrity, and availability impact.
Likely exposure
Organizations running the affected Windows client or server versions are exposed, especially where standard users, service accounts, or malware can execute local code. The source bundle does not identify specific vulnerable components beyond Win32k or list affected builds beyond the supplied Microsoft products.
Exploitation context
CISA KEV status supports that this vulnerability has been exploited in the wild. The available source bundle does not provide exploit mechanics, campaign details, or indicators, so validation should focus on patch state and endpoint telemetry rather than assumed exploit behavior.
Researcher notes
The evidence supports local elevation of privilege in Win32k with KEV-listed exploitation. The bundle lacks CWE mapping, root-cause detail, exploit prerequisites beyond CVSS, and detailed remediation package data. Avoid assuming unsupported affected versions or exploit chains.
Mitigation direction
- Apply Microsoft security updates for CVE-2021-41357 across affected Windows clients and servers.
- Prioritize shared servers, admin workstations, and systems where low-privileged accounts can run code.
- Use endpoint controls to limit untrusted local code execution until patching is complete.
- Check Microsoft guidance for exact update packages and any supersedence details.
Validation and detection
- Inventory Windows versions and builds against the affected product list in the source bundle.
- Verify installation of Microsoft updates covering CVE-2021-41357 on each affected asset.
- Review endpoint alerts for suspicious local privilege escalation activity around untrusted processes.
- Confirm vulnerability scanners or patch tools no longer report CVE-2021-41357.
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-2021-41357 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
- Yes
- Published
Vector: CVSS:3.1/AV:L/AC:L/PR:L/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:L/UI:N/S:U/C:H/I:H/A:H/E:F/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:F/RL:O/RC:C
Source materials
- CVE List V5 sourceCVE List V5
- https://portal.msrc.microsoft.com/en-US/security-guidance/advisory/CVE-2021-41357CVE reference · x_refsource_MISC
- https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2021-41357CVE 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.