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Fencer Vulns
high 7.5

CVE-2026-103577 json

Microsoft QUIC Security Feature Bypass Vulnerability

published 2026-10-13 26 d ago modified 2026-10-31 8 d ago also EUVD-2026-100390

cvss
7.5
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
0.6%
EPSS 0.6% chance of exploitation in 30 days, percentile 47%
public exploits
0
none known

Summary

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

Patch / fix

  • Microsoft Windows 11 version 23H2 10.0.22631.7652
  • Microsoft Windows 11 Version 24H2 10.0.26100.9711
  • Microsoft Windows 11 Version 25H2 10.0.26200.9711
  • Microsoft Windows 11 version 26H1 10.0.28000.3231
  • Microsoft Windows 11 Version 26H2 10.0.26300.9711
  • Microsoft Windows Server 2022 10.0.20348.5761
  • Microsoft Windows Server 2025 10.0.26100.33650
  • Microsoft Windows Server 2025 (Server Core installation) 10.0.26100.33650

CISA SSVC

Exploitation
none
Automatable
no
Technical impact
partial
Assessed
26 d ago

Exploit prediction

0.57% chance of exploitation in the next 30 days, higher than 47% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by version score vector
CNA 3.1 7.5 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
CNA 3.1 7.5 CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:N/I:L/A:H

Affected products

  • Microsoft Windows 11 version 23H2
  • Microsoft Windows 11 Version 24H2
  • Microsoft Windows 11 Version 25H2
  • Microsoft Windows 11 version 26H1
  • Microsoft Windows 11 Version 26H2
  • Microsoft Windows Server 2022
  • Microsoft Windows Server 2025
  • Microsoft Windows Server 2025 (Server Core installation)

Classification

Weakness
  • CWE-453 Insecure Default Variable Initialization

References

Sources

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.