Security readout for executives and security teams
Plain-English summary
A flaw in Windows Remote Access Connection Manager can let someone with local access crash the service, disrupting remote-access connectivity. It does not expose data or alter systems according to the supplied scoring, but service interruption could affect users and operations.
Executive priority
Treat as a high-priority patching issue because CISA KEV status indicates exploitation, despite the medium CVSS score. Expedite remediation on remote-access infrastructure and critical Windows systems, while recognizing that the documented consequence is service disruption rather than data theft or system compromise.
Technical view
CVE-2026-21525 is a CWE-476 null-pointer dereference causing local denial of service. It requires no privileges or user interaction and has low attack complexity. CVSS 3.1 is 6.2, with availability impact rated high and no stated confidentiality or integrity impact.
Likely exposure
Exposure exists on the listed Windows 10, Windows 11, and Windows Server releases where the vulnerable Remote Access Connection Manager component remains unpatched. Prioritize systems supporting VPN, dial-up, or other remote-access operations. The supplied sources do not establish whether the service must be running or specially configured.
Exploitation context
The supplied bundle marks this CVE as present in CISA's Known Exploited Vulnerabilities catalog, supporting active exploitation. Exploitation is local rather than remote and requires neither privileges nor user interaction. The sources provide no campaign scope, attacker attribution, or confirmed impact beyond denial of service.
Researcher notes
The vulnerability is described only as a local null-pointer dereference in Remote Access Connection Manager. The supplied vector is AV:L/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H. Public evidence provided here does not explain the vulnerable code path, crash persistence, prerequisite configuration, or exploitation telemetry. Some affected-product naming appears inconsistent and should be verified against Microsoft.
Mitigation direction
- Install the applicable Microsoft security update identified in the vendor advisory.
- Prioritize remote-access servers and operationally critical Windows endpoints.
- If immediate patching is impossible, consult Microsoft guidance for supported mitigations or workarounds.
- Restrict local access to affected systems until remediation is complete.
Validation and detection
- Inventory affected Windows editions and compare installed builds and updates with Microsoft guidance.
- Confirm the applicable Microsoft security update installed successfully.
- Verify Remote Access Connection Manager and dependent remote-access workflows operate normally after remediation.
- Monitor affected systems for unexpected service crashes or repeated availability disruptions.
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.