CVERadar
MEDIUM · CVSS 3.1 6.2CISA KEV · added 2026-02-10EPSS 4.83% (p92)Threat level 47

CVE-2026-21525: Microsoft Windows NULL Pointer Dereference Vulnerability

Microsoft · Windows · NVD published 2026-02-11 · posted 2026-02-10 · last modified 2026-06-17

What it is

Null pointer dereference in Windows Remote Access Connection Manager allows an unauthorized attacker to deny service locally.

WeaknessCWE-476
CVSS vectorCVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H (source: [email protected])
CISA due date2026-03-03 (for US federal agencies under BOD; a good deadline for everyone)
ATT&CK tacticsImpact

Exploitation evidence

First exploit evidence seen: 2026-02-10 (earliest date across the sources below).

Exploited in the wild

  • CISA KEV: listed since 2026-02-10. Source

Sources: CISA KEV.

Defend the Chain

The attack chain for CVE-2026-21525 laid across the MITRE ATT&CK Enterprise tactics. Solid cards come from the MITRE CTID KEV mappings; dashed cards are inferred by CVERadar from the CWE or description. Correct defences are real ATT&CK mitigations for that technique.

Threat level 47/100
Defender level 1 · 0 XP
Chain links broken: 0/1

Reconnaissance

Resource Development

Initial Access

Execution

Persistence

Privilege Escalation

Stealth

Defense Impairment

Credential Access

Discovery

Lateral Movement

Collection

Command and Control

Exfiltration

Impact

Pick a red technique card on the board, then choose the defence that stops it.

Defend against T1499 Endpoint Denial of Service Inferred

Inferred from CWE CWE-476

How to fix it

CISA required action

Apply mitigations per vendor instructions, follow applicable BOD 22-01 guidance for cloud services, or discontinue use of the product if mitigations are unavailable. (source: CISA KEV)

Fixed versions

  • microsoft windows 10 1607: upgrade to 10.0.14393.8868 or later
  • microsoft windows 10 1809: upgrade to 10.0.17763.8389 or later
  • microsoft windows 10 21h2: upgrade to 10.0.19044.6937 or later
  • microsoft windows 10 22h2: upgrade to 10.0.19045.6937 or later
  • microsoft windows 11 23h2: upgrade to 10.0.22631.6649 or later
  • microsoft windows 11 24h2: upgrade to 10.0.26100.7781 or later
  • microsoft windows 11 25h2: upgrade to 10.0.26200.7781 or later
  • microsoft windows server 2016: upgrade to 10.0.14393.8868 or later
  • microsoft windows server 2019: upgrade to 10.0.17763.8389 or later
  • microsoft windows server 2022: upgrade to 10.0.20348.4711 or later
  • microsoft windows server 2022 23h2: upgrade to 10.0.25398.2149 or later
  • microsoft windows server 2025: upgrade to 10.0.26100.32313 or later

Derived from the NVD CPE configuration (versionEndExcluding / versionEndIncluding). Always confirm with the vendor advisory.

Vendor advisories and patches

MITRE ATT&CK mitigations for this chain

  • M1037 Filter Network Traffic (for T1499) : Leverage services provided by Content Delivery Networks (CDN) or providers specializing in DoS mitigations to filter traffic upstream from services. Filter boundary traffic by blocking source addresses sourcing the attack, blocking ports that are being targeted, or blocking protocols being used for transport. To defend

Detection Generic guidance

  • Impact: Monitor service availability, unexpected encryption activity and mass file changes.

Response checklist Generic guidance

  1. Inventory: find every instance of the affected product and version (include internet-facing and forgotten ones).
  2. Patch or mitigate per the vendor advisory; if you cannot patch, remove internet exposure or apply the vendor workaround.
  3. Assume compromise if the system was exposed before patching: hunt for the indicators in the advisory and review logs back to the disclosure date.
  4. Rotate credentials and secrets stored on or used by the affected system if compromise cannot be ruled out.

Sources