Security readout for executives and security teams
Plain-English summary
This flaw can let a low-privileged attacker elevate privileges in Microsoft Active Directory Domain Services, potentially compromising identities and systems across a Windows domain. Successful exploitation requires network access and higher attack complexity, but no user interaction. CISA lists the vulnerability as known exploited, making prompt remediation important.
Executive priority
Treat remediation as urgent because Active Directory is identity-critical and CISA records active exploitation. Require rapid inventory, patch verification, and escalation of unsupported or unpatchable servers. The 7.5 score understates potential business impact if domain privileges or central identity services are compromised.
Technical view
CVE-2021-42287 is an Active Directory Domain Services elevation-of-privilege vulnerability affecting listed Windows Server releases from 2008 SP2 through 2022, including several Server Core installations. CVSS 3.1 is 7.5: network-accessible, high complexity, low privileges required, no user interaction, and high confidentiality, integrity, and availability impact.
Likely exposure
Exposure is most likely where listed Windows Server versions run Active Directory Domain Services and lack the applicable Microsoft security update. The bundle does not provide fixed-build numbers, update identifiers, configuration prerequisites, or a reliable remote exposure test, so organizations must compare deployments with Microsoft’s advisory.
Exploitation context
CISA KEV status supports that this vulnerability has been exploited in the wild. The supplied evidence does not describe exploitation prevalence, current campaigns, targets, or whether exploitation commonly occurs alone or in a chain. Low privileges are required, while the CVSS vector indicates high attack complexity.
Researcher notes
The bundle provides CVSS characteristics, affected products, a Microsoft patch reference, and KEV status, but no CWE, root-cause detail, fixed builds, indicators, or campaign evidence. Validation should therefore remain version-and-update based. Do not infer a specific exploitation technique or relationship to other CVEs from this evidence alone.
Mitigation direction
- Inventory Active Directory systems running the listed Windows Server releases, including Server Core installations.
- Apply the applicable Microsoft security update identified in the MSRC advisory.
- Prioritize domain controllers and other identity-critical servers for accelerated remediation.
- Follow Microsoft guidance for any deployment prerequisites or additional mitigations.
- Restrict unnecessary network access to affected systems until remediation is verified.
Validation and detection
- Compare every Active Directory server’s operating system and update status with the MSRC advisory.
- Confirm the applicable security update is installed across all affected identity infrastructure.
- Use authenticated vulnerability scanning or update-management records to identify missed systems.
- Review identity and administrative logs for unexplained privilege changes or suspicious account activity.
- Document exceptions where unsupported systems cannot receive the applicable update.
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-2021-42287 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
- 7.5 (3.1)
- Known Exploited
- Yes
- Published
Vector: CVSS:3.1/AV:N/AC:H/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.
CISA KEV status
SSVC decision data
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:N/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H/E:U/RL:O/RC:C1.65.9microsoftVulnerability scoring details
Base CVSS 3.1 score
7.5HighVector: CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H/E:U/RL:O/RC:C
Vulnerability timeline
Timeline events are normalized from CVE metadata, CNA source timelines, ADP timelines, and KEV metadata when present.
- CVE reservedCVE Program
The CVE ID was reserved by the assigning CNA.
- CVE publishedCVE Program
The CVE record was published.
- Added to KEVCISA-ADP
CISA Known Exploited Vulnerabilities metadata lists this CVE as known exploited.
- CVE updatedCVE Program
The CVE record metadata indicates this as the latest update time.
ADP provider summaries
Source materials
- CVE List V5 sourceCVE List V5
- Active Directory Domain Services Elevation of Privilege VulnerabilityCVE reference, microsoft · vendor-advisory, patch
- https://portal.msrc.microsoft.com/en-US/security-guidance/advisory/CVE-2021-42287CVE reference, CVE · x_refsource_MISC, x_transferred
- https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2021-42287CVE reference, CISA-ADP · 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.