Microsoft QUIC: Integer underflow causes denial of service
Summary
An integer underflow (CWE-191) in Microsoft QUIC, the QUIC transport stack in Windows, allows an unauthenticated remote attacker to cause a denial of service. The attack requires only network access to a system that accepts QUIC traffic, with no privileges or user interaction. The impact is limited to availability; no loss of confidentiality or integrity is reported.
Affected
- Windows 11 version 23H2: 10.0.22631.0 to before 10.0.22631.7711
- Windows 11 version 24H2: 10.0.26100.0 to before 10.0.26100.9974
- Windows 11 version 25H2: 10.0.26200.0 to before 10.0.26200.9974
- Windows 11 version 26H1: 10.0.28000.0 to before 10.0.28000.3501
- Windows 11 version 26H2: 10.0.26300.0 to before 10.0.26300.9974
- Windows Server 2022: 10.0.20348.0 to before 10.0.20348.5870
- Windows Server 2025 (including Server Core): 10.0.26100.0 to before 10.0.26100.33822
- Windows 10 and older Windows Server versions: Unknown.
Fixed in
- Install the Windows security update of the November 2026 Patch Tuesday (released 10 November 2026) or later.
- Fixed builds: Windows 11 23H2 10.0.22631.7711; 24H2 10.0.26100.9974; 25H2 10.0.26200.9974; 26H1 10.0.28000.3501; 26H2 10.0.26300.9974; Windows Server 2022 10.0.20348.5870; Windows Server 2025 10.0.26100.33822.
Workaround
- No vendor workaround found. Status: unknown.
- If QUIC or HTTP/3 is not required, block inbound UDP/443 at the perimeter. This is not a Microsoft recommendation; check the impact on your services first.
Exploitation
- No evidence of exploitation in the wild found in the sources checked.
- Not found in the CISA KEV catalogue in the sources checked.
- No public proof of concept found.
- CISA SSVC assessment: exploitation none, automatable yes, technical impact partial.
Our recommendation
- Install the November 2026 security update on affected Windows 11 and Windows Server systems in the regular patch cycle, with priority for internet-facing servers.
- Check whether QUIC (UDP/443) is reachable from the internet and restrict it where it is not needed.
- Monitor affected systems for unexpected crashes or availability problems.
- Verify the affected product list against the MSRC advisory before relying on version details.
Information from Microsoft (Patch Tuesday November 2026)
Public exploits
PoC-in-GitHub, Metasploit and Exploit-DB list nothing for this CVE.
Research sources
- CVE Record CVE-2026-105512 www.cve.org
- Microsoft Security Update Guide (MSRC) msrc.microsoft.com
- Strix AI CVE details (product and version list, unverified) www.strix.ai
- Rapid7 Patch Tuesday November 2026 review www.rapid7.com
Researched and written up in English and German by an AI (Claude by Anthropic) based on NVD, CISA, EPSS and the sources listed. The vendor information is authoritative. Researched on 11 Nov 2026, 06:13.
Original description (NVD)
Integer underflow (wrap or wraparound) in Microsoft QUIC allows an unauthorized attacker to deny service over a network.
NVD references (1)
Sources
The tracker combines official, freely usable data sources – updated continuously:
- NVD (NIST) – CVEs, rating (CVSS), affected products
- CISA KEV – vulnerabilities confirmed by CISA as actively exploited
- CISA Vulnrichment – CISA assessment (SSVC) in the official CVE record
- FIRST EPSS – probability of exploitation
- Microsoft MSRC – Patch Tuesday: vulnerabilities, severity, updates
- PoC-in-GitHub – public proof-of-concept repositories
- Metasploit (Rapid7) – modules of the Metasploit Framework
- Exploit-DB (OffSec) – archive of public exploits (links only)
- Patch days: official vendor pages (linked per vendor) (Vendor patch days)
This product uses data from the NVD API but is not endorsed or certified by the NVD. EPSS data © FIRST.org.
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