High

Windows Subsystem for Linux Use-After-Free Privilege Escalation

IdentifiersCVE-2026-21242CWE-416· Use After Free

CVE-2026-21242 is a local elevation-of-privilege vulnerability in Windows Subsystem for Linux (WSL). The provided content identifies the flaw as a use-after-free condition in WSL. An authorized local attacker can exploit this memory-lifecycle error to elevate privileges on the affected Windows system. No further technical detail about the specific vulnerable function, code path, or triggering sequence is provided in the supplied content.

For your environment

Are you exposed to this one?

Mallory correlates every CVE against your assets, your vendors, and active adversary campaigns. Know which vulnerabilities matter for you, not just which ones are loud.

Start free trial

ANALYST BRIEF

Impact, mitigation & remediation

What it means. What to do now. Patch path, mitigations, and the assume-compromise checklist.

Impact

What an attacker gets, and what they’ve been doing with it.

Successful exploitation allows local privilege escalation on an affected Windows host running WSL. The attacker must already have authorized local access, after which the vulnerability can be used to obtain higher privileges than initially assigned.

Mitigation

If you can’t patch tonight, do this now.

If immediate patching is not possible, reduce exposure by limiting local access to trusted users only and restricting use of affected WSL-enabled systems where feasible until updates are applied. No vulnerability-specific workaround or vendor mitigation is provided in the supplied content.

Remediation

Patch, then assume compromise.

Apply Microsoft's February 2026 security updates for affected supported Windows versions, including the patch covering CVE-2026-21242. The supplied content indicates Microsoft released patches for supported product versions and recommends prompt installation, with verification through Windows Update, Update History, or the Microsoft Update Catalog if needed.

PUBLIC EXPLOITS

Exploits

No public exploits tracked yet. Mallory keeps watching.

VALID 0 / 0 TOTALView more in app

No public exploit code observed for this vulnerability.

EXPOSURE SURFACE

Affected products & vendors

Products and vendors Mallory has correlated with this vulnerability. Open in Mallory to drill down to specific CPE configurations and version ranges.

VendorProductType

Microsoft CorporationWindows 10 21h2operating_system

Microsoft CorporationWindows 10 22h2operating_system

Microsoft CorporationWindows 11 23h2operating_system

Microsoft CorporationWindows 11 24h2operating_system

Microsoft CorporationWindows 11 25h2operating_system

Microsoft CorporationWindows 11 26h1operating_system

Microsoft CorporationWindows Server 2022operating_system

Microsoft CorporationWindows Server 2022 23h2operating_system

Microsoft CorporationWindows Server 2025operating_system

Microsoft CorporationWindows Server 23h2operating_system

Vendor-confirmed product mapping. Mallory continuously reconciles this list against your asset inventory.

ACTIVITY FEED

Recent activity

6 sources tracked across advisories, community write-ups, and news. New activity surfaces here as Mallory finds it.

6 SOURCESView more in app

nsfocus globalNews

Mar 4, 2026

Microsoft’s February Security Update of High-Risk Vulnerability Notice for Multiple Products - NSFOCUS, Inc., a global network and cyber security leader, protects enterprises and carriers from advanced cyber attacks.

A privilege escalation vulnerability affecting Windows Subsystem for Linux (WSL).

bleeping computerNews

Feb 10, 2026

Microsoft February 2026 Patch Tuesday fixes 6 zero-days, 58 flaws

An elevation of privilege vulnerability in Windows Subsystem for Linux (no additional details provided in the content).

zerodayinitiative blogNews

Feb 10, 2026

Zero Day Initiative - The February 2026 Security Update Review

An elevation of privilege vulnerability in Windows Subsystem for Linux (WSL).

What this page doesn’t show

The version that knows your environment.

This page is what’s public. Mallory adds the parts that aren’t: which of your assets are affected, which adversaries are exploiting it right now, which detections to deploy, and what to do tonight.

Start free trial

Exposure mapping

Query your assets running an affected version, and investigate the blast radius.

Threat actor evidence

Every observed campaign linking this CVE to a named adversary.

Associated malware

Malware families riding this exploit, with evidence and IOCs.

Detection signatures

YARA, Sigma, Snort, and vendor rules, auto-deployed to your SIEM.

Vendor-by-vendor mapping

Cross-references every affected SKU, including bundled OEM variants.

Social activity2