Security readout for executives and security teams
Plain-English summary
This flaw can let a local, unauthenticated attacker crash or disrupt Windows Remote Access Connection Manager. It does not expose data or enable remote takeover in the provided sources, but CISA KEV status raises urgency because known exploitation is reported.
Executive priority
Treat as urgent patch management, not a breach indicator by itself. The business risk is service disruption on Windows systems, with priority elevated by CISA KEV listing and broad platform coverage.
Technical view
CVE-2026-21525 is a CWE-476 null pointer dereference in Windows Remote Access Connection Manager. CVSS 3.1 is 6.2 with local attack vector, low complexity, no privileges, no user interaction, and high availability impact only.
Likely exposure
Exposure is broad across listed Windows 10, Windows 11, and Windows Server 2012 through 2022 versions, including Server Core variants. Systems using or running Remote Access Connection Manager deserve priority review.
Exploitation context
The source bundle marks this CVE as CISA KEV, supporting known exploitation. Microsoft scoring in the bundle lists exploit code maturity as unproven, so public technical details appear limited from the provided evidence.
Researcher notes
Focus validation on affected OS build mapping, service presence, and patch state. Avoid assuming remote exploitability; the provided CVSS vector is local. Evidence does not support confidentiality or integrity impact.
Mitigation direction
- Apply Microsoft security updates from the MSRC advisory.
- Prioritize internet-adjacent, remote-access, and critical Windows servers.
- Check Microsoft guidance for any product-specific workarounds.
- Track CISA KEV remediation deadlines in vulnerability management.
- Validate patch coverage across Server Core and workstation builds.
Validation and detection
- Inventory Windows versions against the affected product list.
- Confirm the relevant Microsoft update is installed.
- Identify systems running Remote Access Connection Manager.
- Review availability incidents involving remote access services.
- Document exceptions and compensating controls for unpatched 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.
CWE-476: Exact CWE lookup
Use the exact CWE identifier as the starting point before reviewing related ATT&CK behavior. Open the exact CWE lookup page first, then review the ATT&CK searches from that MITRE weakness context. This is a Glexia lookup hint, not an official ATT&CK mapping.
Open ATT&CK lookupCVE-2026-21525 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
- Medium
- CVSS
- 6.2 (3.1)
- Known Exploited
- Yes
- Published
Vector: CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:N/I:N/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:L/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H/E:U/RL:O/RC:C2.53.6microsoftVulnerability scoring details
Base CVSS 3.1 score
6.2MediumVector: CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:N/I:N/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.
- Added to KEVCISA-ADP
CISA Known Exploited Vulnerabilities metadata lists this CVE as known exploited.
- ADP timelineCISA-ADP
CVE-2026-21525 added to CISA KEV
- 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
- 2026-02-10T00:00:00.000Z: CVE-2026-21525 added to CISA KEV
Source materials
- CVE List V5 sourceCVE List V5
- Windows Remote Access Connection Manager Denial of Service VulnerabilityCVE reference, microsoft · vendor-advisory, patch
- https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2026-21525CVE reference, CISA-ADP · government-resource
- https://www.vicarius.io/vsociety/posts/cve-2026-21525-detection-script-dos-vulnerability-in-windows-remote-access-connection-managerCVE reference, CVE
- https://www.vicarius.io/vsociety/posts/cve-2026-21525-mitigation-script-dos-vulnerability-in-windows-remote-access-connection-managerCVE reference, CVE
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.
NULL Pointer Dereference
NULL Pointer Dereference represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.