High 7.5Published Oct 13, 2026

CVE-2026-103577Microsoft QUIC Security Feature Bypass Vulnerability

Updated under an hour ago (Oct 27, 2026, 10:30 PM ET)

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It affects Microsoft Windows 11 version 23H2 and 6 other products. Add what you run to find out whether that includes you.

EPSS puts the chance of exploitation in the next 30 days at 0.59%, higher than 48% of scored CVEs.

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Every CVE for Microsoft Windows 11 version 23H2

Exploited in the last 30 days

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

CVSS: 7.5 HIGH (v3.1, CNA)CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:N/I:L/A:H/E:U/RL:O/RC:C
Weakness (CWE): CWE-453
Known exploited: Not in CISA's KEV catalog
EPSS (exploitation in the next 30 days): 0.59% (percentile 48)
Assigned by: microsoft
NVD analysis: Analyzed
Record last updated: Oct 27, 2026
First seen by InfoSec Signals: Oct 13, 2026

Affected products

Affected products

Microsoft Windows 11 version 23H2 microsoft:windows_11_23h2	from 10.0.22631.0 before 10.0.22631.7652	CNA record
Microsoft Windows 11 Version 24H2 microsoft:windows_11_24h2	from 10.0.26100.0 before 10.0.26100.9711	CNA record
Microsoft Windows 11 Version 25H2 microsoft:windows_11_25h2	from 10.0.26200.0 before 10.0.26200.9711	CNA record
Microsoft Windows 11 version 26H1 microsoft:windows_11_26h1	from 10.0.28000.0 before 10.0.28000.3231	CNA record
Microsoft Windows 11 Version 26H2 microsoft:windows_11_26h2	from 10.0.26300.0 before 10.0.26300.9711	CNA record
Microsoft Windows Server 2022 microsoft:windows_server_2022 (from the name)	from 10.0.20348.0 before 10.0.20348.5761	CNA record
Microsoft Windows Server 2025 microsoft:windows_server_2025 (from the name)	from 10.0.26100.0 before 10.0.26100.33650	CNA record
microsoft windows_11_23h2 microsoft:windows_11_23h2	before 10.0.22631.7652; before 10.0.22631.7652	NVD
microsoft windows_11_24h2 microsoft:windows_11_24h2	before 10.0.26100.9711; before 10.0.26100.9711	NVD
microsoft windows_11_25h2 microsoft:windows_11_25h2	before 10.0.26200.9711; before 10.0.26200.9711	NVD
1–10 of 14

References

References

https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-103577	vendor-advisory, patch

The CVE record on cve.org NVD's entry

The CVE record is authoritative. Products marked “from the name” were identified from the CNA's free-text names, not a CPE, and are matched less certainly. This product uses the NVD API but is not endorsed or certified by the NVD.