Security readout for executives and security teams
Plain-English summary
An unauthenticated attacker who can reach an affected Windows DNS Server could remotely run code without user involvement. Successful exploitation could compromise the server’s data, integrity, and availability. Because DNS servers often support essential operations, disruption or takeover could have substantial business impact.
Executive priority
Treat remediation as urgent wherever listed Windows Server releases provide DNS. The vulnerability permits unauthenticated, low-complexity network RCE with potentially complete system impact, although active exploitation is not established by the supplied evidence.
Technical view
CVE-2021-26894 is a network-accessible remote code execution vulnerability in listed Windows Server DNS implementations. Its CVSS 3.1 score is 9.8, with low attack complexity, no required privileges, and no user interaction. The supplied vector rates confidentiality, integrity, and availability impacts as high.
Likely exposure
Exposure is limited to listed Windows Server releases operating as DNS servers, including Server Core installations from Windows Server 2008 through version 20H2. Risk is greatest when the DNS service is reachable from untrusted networks. The bundle does not identify specific configurations that eliminate exposure.
Exploitation context
The supplied record does not establish active exploitation, and the CVE is not identified as a CISA KEV entry. No public exploit, attack campaign, or indicators of compromise are documented in the provided sources. Absence from KEV does not reduce the underlying technical severity.
Researcher notes
The bundle supplies no CWE, root-cause analysis, vulnerable protocol details, proof of concept, or exploitation telemetry. Product coverage and severity are well supported, but researchers should consult Microsoft’s advisory for exact update applicability and any subsequently published technical guidance.
Mitigation direction
- Inventory listed Windows Server releases and identify systems providing DNS services.
- Apply Microsoft’s security update for each affected Windows Server release.
- Prioritize externally reachable and business-critical DNS servers for remediation.
- Restrict DNS service reachability to required clients while updates are pending.
- Consult Microsoft guidance for supported mitigations if immediate patching is impossible.
Validation and detection
- Confirm whether the DNS Server role is enabled on each potentially affected system.
- Verify installed security updates against Microsoft’s CVE advisory for the exact release.
- Test whether affected DNS services are reachable from untrusted network segments.
- Review DNS server and endpoint alerts for anomalies; the sources provide no specific indicators.
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.
Execution behavior lookup
The CVE wording references code or command execution, so execution technique review may help defensive triage. This is a Glexia inferred lookup path, not an official MITRE, ATT&CK, or CVE Program mapping.
Open ATT&CK lookupCVE-2021-26894 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
- Critical
- CVSS
- 9.8 (3.1)
- Known Exploited
- No
- Published
Vector: CVSS:3.1/AV:N/AC:L/PR:N/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:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H/E:U/RL:O/RC:C3.95.9microsoftVulnerability scoring details
Base CVSS 3.1 score
9.8CriticalVector: CVSS:3.1/AV:N/AC:L/PR:N/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.
- 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
- Windows DNS Server Remote Code Execution VulnerabilityCVE reference, microsoft · vendor-advisory, patch
- https://portal.msrc.microsoft.com/en-US/security-guidance/advisory/CVE-2021-26894CVE reference, CVE · 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.