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Mallory
Medium

Denial of Service in Windows VMSwitch/TCP-IP Buffer Size Calculation

IdentifiersCVE-2026-42915CWE-131· Incorrect Calculation of Buffer Size

CVE-2026-42915 is a denial-of-service vulnerability caused by incorrect calculation of buffer size in a Windows networking component. The provided content is inconsistent on the affected component, referring to both Windows VMSwitch and Windows TCP/IP, but consistently describes the flaw as an incorrect buffer size calculation. Microsoft advisory-derived text states that an authorized attacker can exploit the issue from an adjacent network to cause denial of service on the affected Windows system.

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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 an authorized attacker to crash or otherwise disrupt the affected Windows system or networking service, resulting in denial of service. The supplied advisory text indicates the attack can be carried out from an adjacent/LAN network and does not describe code execution, privilege escalation, or data disclosure.

Mitigation

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

No vendor-supplied mitigation is provided in the available content. As an interim risk-reduction measure, restrict exposure of affected systems to untrusted adjacent/LAN segments, enforce network access controls to limit who can reach vulnerable hosts over the local network, and monitor for anomalous traffic that may target the Windows TCP/IP stack until patches are deployed.

Remediation

Patch, then assume compromise.

Apply Microsoft's June 2026 security update for CVE-2026-42915 to affected Windows systems.
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 CorporationWindowsoperating_system
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 2025operating_system

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

ACTIVITY FEED

Recent activity

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

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.
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 activity8

Community discussion across Reddit, Mastodon, and other social sources.