Threat Intelligence / CVE / CVE-2026-21533

CVE-2026-21533 — Microsoft Windows 10 1607

CISA KEV
CVSS v3.1 7.8 (HIGH) · EPSS 22.7% (higher than 95.8% of all scored CVEs) · Priority 9/10 · Published 2026-02-10

As of 2026-03-30, CVE-2026-21533 is a HIGH-severity vulnerability in Microsoft Windows 10 1607, CVSS v3.1 7.8, EPSS 22.7% (95.8th percentile). It is listed in the CISA Known Exploited Vulnerabilities catalog (added 2026-02-10), with a US federal remediation deadline of 2026-03-03. Threadlinqs Intelligence links 2 tracked threat campaigns to CVE-2026-21533, most recently “February 2026 Patch Tuesday: Six Zero-Days Among 59 CVEs — CrowdStrike-Discovered RDP EoP Exploited Since December 2025”.

Last updated: 2026-03-30

What is CVE-2026-21533?

Improper privilege management in Windows Remote Desktop allows an authorized attacker to elevate privileges locally.

The record classifies CVE-2026-21533 under weakness class CWE-269. Its CVSS v3 base vector states that the flaw requires local access to the host, needs low-privilege credentials, needs no user interaction, and has high impact on confidentiality, integrity, availability. 23 affected-product entries are recorded, across 1 vendor, listed below. The identifier was first published 215 days ago.

Severity and exploitation probability

CVSS v3.1 base score
7.8 — HIGH
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
EPSS (FIRST)
22.7% probability of exploitation in the next 30 days, higher than 95.8% of all scored CVEs
CISA KEV
Listed since 2026-02-10, federal remediation deadline 2026-03-03
Threadlinqs priority
9/10 — CISA KEV-listed, which Threadlinqs floors at 9
Published
2026-02-10, last modified 2026-03-30

Is CVE-2026-21533 being exploited?

CISA added CVE-2026-21533 to the Known Exploited Vulnerabilities catalog on 2026-02-10, which means the agency holds evidence of exploitation in the wild; US federal civilian agencies had to remediate it by 2026-03-03 under BOD 22-01. It currently carries a trending score of 44 in the Threadlinqs vulnerability feed.

Affected products and versions

Showing 14 of 23 recorded product entries.

How to fix CVE-2026-21533

Vendor advisory: https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-21533. Because CVE-2026-21533 is KEV-listed, US federal civilian agencies were required to apply the vendor fix, or stop using the product, by 2026-03-03. Apply the vendor fix referenced above to every affected product listed in this record, then confirm the running version against the vendor advisory.

Threat activity tracking CVE-2026-21533

2 tracked threats in the Threadlinqs corpus reference CVE-2026-21533, either in the campaign’s CVE list or as an indicator on the campaign record.

Sources

Seeded from nvd and not yet processed by the Threadlinqs enrichment pipeline, so blank CVSS, EPSS or KEV fields above mean NOT MEASURED rather than measured-absent.

Full detection coverage & IOCs for threats exploiting CVE-2026-21533 are available via the Threadlinqs MCP server (Purple tier). View plans →

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