VulnerabilityAnalyzed
CVE-2026-103577
Insecure default variable initialization in Microsoft QUIC allows an unauthorized attacker to bypass a security feature over a network.
HIGH 7.5EPSS 0.59%
Does this matter?
High impact if exploited, but EPSS currently rates exploitation as unlikely (0.59%). Schedule it in the normal patch cycle and watch for a rise in EPSS or a public exploit.
Description
Insecure default variable initialization in Microsoft QUIC allows an unauthorized attacker to bypass a security feature over a network.
- CVSS 3.1
- 7.5 HIGHCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:N/I:L/A:H
- EPSS
- 0.59% probability · 48th percentile
- Public exploits
- None in Exploit-DB
- CISA KEV
- Not listed
- Weakness
- CWE-453
- Affected
- microsoft/windows 11 23h2 · microsoft/windows 11 24h2 · microsoft/windows 11 25h2 · microsoft/windows 11 26h1 · microsoft/windows 11 26h2 · microsoft/windows server 2022 · microsoft/windows server 2025
- Source
- secure@microsoft.com
EPSS moved from 0.5% on 14 October 2026 to 0.6% on 26 October 2026.
References
- https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-103577Patch, Vendor Advisory
Source: NVD record, EPSS from FIRST.org, KEV from CISA, exploits from Exploit-DB. Refreshed daily. Download this record as JSON.