Security Digest · Vulnerability record · Known exploited
CVE-2026-21525: Microsoft Windows NULL Pointer Dereference Vulnerability
Exploited in the wild (CISA KEV). Null pointer dereference in Windows Remote Access Connection Manager allows an unauthorized attacker to deny service locally.
CISA KEV · added 2026-02-10 CVSS 6.2 Medium EPSS 4.8% · p92
Should you act?
Exploited: patch now if you run it
CISA has confirmed exploitation in the wild. This signal is computed from CISA KEV, EPSS and CVSS data; it is not an editorial verdict.
- Yes, if you run Microsoft Windows. CISA added this CVE to its Known Exploited Vulnerabilities catalog on 2026-02-10, which means there is reliable evidence of exploitation in the wild. US federal agencies must remediate by 2026-03-03; treat that as the outer limit, not the target.
- EPSS 4.8%, percentile 92: FIRST’s model estimates a 4.8% chance of exploitation activity in the next 30 days, higher than 92% of all scored CVEs (elevated). EPSS is a probability, not a verdict.
- Needs local access needed. Lower urgency for most teams unless an attacker could already run code on the machine.
What it is
Null pointer dereference in Windows Remote Access Connection Manager allows an unauthorized attacker to deny service locally.
CISA’s summary
Microsoft Windows Remote Access Connection Manager contains a NULL pointer dereference that could allow an unauthorized attacker to deny service locally.
Weakness type: CWE-476.
Product: Microsoft Windows · Assigned by: microsoft · Published: 2026-02-10
Affected and fixed versions
| Vendor | Product | Affected versions (per CVE record) |
|---|---|---|
| Microsoft | Windows 10 Version 1607 | 10.0.14393.0 < 10.0.14393.8868 |
| Microsoft | Windows 10 Version 1809 | 10.0.17763.0 < 10.0.17763.8389 |
| Microsoft | Windows 10 Version 21H2 | 10.0.19044.0 < 10.0.19044.6937 |
| Microsoft | Windows 10 Version 22H2 | 10.0.19045.0 < 10.0.19045.6937 |
| Microsoft | Windows 11 version 22H3 | 10.0.22631.0 < 10.0.22631.6649 |
| Microsoft | Windows 11 Version 23H2 | 10.0.22631.0 < 10.0.22631.6649 |
| Microsoft | Windows 11 Version 24H2 | 10.0.26100.0 < 10.0.26100.7840 |
| Microsoft | Windows 11 Version 25H2 | 10.0.26200.0 < 10.0.26200.7840 |
| Microsoft | Windows 11 version 26H1 | 10.0.28000.0 < 10.0.28000.1575 |
| Microsoft | Windows 11 Version 26H1 | 10.0.28000.0 < 10.0.28000.1575 |
Severity scores
| Scored by | CVSS | Score | Vector |
|---|---|---|---|
| microsoft | 3.1 | 6.2 Medium | 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 |
- Attack vector: local access needed
- Attack complexity: low
- Privileges required: none (no login)
- User interaction: none
- Scope: unchanged
CVSS measures how bad a flaw is if exploited, not how likely exploitation is. Read it next to the exploitation data below.
Exploitation and urgency
- CISA KEV: added 2026-02-10; federal due date 2026-03-03. Known ransomware use: Unknown.
- 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.
- CISA SSVC assessment: exploitation active, automatable no, technical impact partial.
- FIRST EPSS (model of 2026-10-21): 4.83% probability of exploitation activity in the next 30 days; percentile 92.
Timeline
- — Added to CISA’s Known Exploited Vulnerabilities catalog
- — CVE record published by microsoft
- — CISA remediation deadline for US federal agencies
- — CVE record last updated
Sources and references
Original sources first. Version and fix details should always be confirmed against the vendor or project advisory.
Vendor and project advisories, patches
- Windows Remote Access Connection Manager Denial of Service Vulnerability msrc.microsoft.com
Vulnerability records
- CVE.org record CVE-2026-21525 cve.org
- NVD entry CVE-2026-21525 nvd.nist.gov
Government
Other references from the CVE record and advisory
- vicarius.io vicarius.io
- vicarius.io vicarius.io
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