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CVE-2026-103577

Microsoft QUIC Security Feature Bypass Vulnerability

No known exploitation. No EPSS score yet. Fixed versions are out.

CVSS 3.17.5HighEPSS percentile—No score yetCISA KEVNot listedNo confirmed exploitation
No public exploit knownFix4 products7 fixed builds listed below

Published Updated Sources: CVE.org, NVD

NVD CVE.org

What to do

Find your product and version, then upgrade to the build on the right.

  • Microsoft Windows 11 version 23H2Affected: ≥ 10.0.22631.0, < 10.0.22631.7652Upgrade to: 10.0.22631.7652Affected: ≥ 10.0.26100.0, < 10.0.26100.9711Upgrade to: 10.0.26100.9711Affected: ≥ 10.0.26200.0, < 10.0.26200.9711Upgrade to: 10.0.26200.9711Affected: ≥ 10.0.28000.0, < 10.0.28000.3231Upgrade to: 10.0.28000.3231Stated by: CVE record
  • Microsoft Windows 11 Version 26H2Affected: ≥ 10.0.26300.0, < 10.0.26300.9711Upgrade to: 10.0.26300.9711Stated by: CVE record
  • Microsoft Windows Server 2022Affected: ≥ 10.0.20348.0, < 10.0.20348.5761Upgrade to: 10.0.20348.5761Stated by: CVE record
  • Microsoft Windows Server 2025Affected: ≥ 10.0.26100.0, < 10.0.26100.33650Upgrade to: 10.0.26100.33650Stated by: CVE record

Versions as the sources state them. Full version matrix after sign-in

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What it is

From the CVE record

Insecure default variable initialization in Microsoft QUIC allows an unauthorized attacker to bypass a security feature over a network.

In plain language

No plain-language summary for this CVE yet.

Exploitation

Where each signal puts this CVE on the scale from published to confirmed exploited.

CISA KEV

Not in the catalog. CISA has not confirmed exploitation.

Public exploits

No public exploit or proof of concept found in the sources we track.

EPSS

No EPSS score yet. New CVEs are usually scored within a few days.

Lifecycle

4 events over 0 days, from the signal feeds we watch.

  1. Publishedweakness classified, record updated, record updated

Affected products

And 5 more affected products. See all after sign-in

Technical detail

CVSS 3.1 vector

Open in the CVSS calculator

CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:N/I:L/A:H

Scored 7.5 by NVD.

How it is reached

  • Attack Vector NetworkExploitable remotely over the network without any special conditions
  • Attack Complexity HighRequires specific conditions like a race condition or non-default configuration
  • Privileges Required NoneNo authentication required — anyone can exploit this
  • User Interaction NoneNo user interaction needed — fully automated exploitation

Scope

  • Scope ChangedThe exploit can affect other components (e.g. sandbox escape, host compromise from VM)

Impact if exploited

  • Confidentiality NoneNo confidentiality impact
  • Integrity LowData modification is possible but limited in scope or consequence
  • Availability HighTotal denial of service — the component is completely unavailable

Weaknesses

Sources

References in the record

In the news

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We'll flag the next CVE, public exploit or patch for Windows 11 version 23H2, not every advisory.