CVE-2026-103577

HIGH

Published Oct 13, 2026 Modified Oct 13, 2026 CWE-453

Description

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

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CVSS v3.1 Score

7.5

HIGH

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

EPSS — Exploit Prediction

0.0052

Probability of exploitation

0.43%

Percentile rank

EPSS estimates the probability that this vulnerability will be exploited in the wild within the next 30 days. A higher score means more likely to be exploited.

Weakness Type (CWE)

CWE-453 CWE-453

References

Other References

https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-103577

Frequently Asked Questions

What is CVE-2026-103577? +

Insecure default variable initialization in Microsoft QUIC allows an unauthorized attacker to bypass a security feature over a network. It has a CVSS v3.1 base score of 7.5 (HIGH).

How severe is CVE-2026-103577? +

CVE-2026-103577 has a CVSS v3.1 score of 7.5 out of 10, rated HIGH. This is a high-severity vulnerability that should be prioritized for patching. The EPSS score is 0.0052, placing it in the 0th percentile for exploitation probability.

How do I check if I'm vulnerable to CVE-2026-103577? +

You can use Secably's free Website Scanner to check your website for known vulnerabilities. For infrastructure scanning, use the Port Scanner to identify exposed services that may be affected. Check the vendor advisories linked above for specific patch and version information.