How severe is CVE-2026-103577?

CVE-2026-103577 has a CVSS 3.x base score of 7.5, rated high severity. It is exploitable over network with high attack complexity, requires no privileges and no user interaction. Impact on confidentiality is none, integrity low, and availability high.

Is CVE-2026-103577 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (43rd percentile), an estimate of the probability of exploitation in the next 30 days.

How do I fix CVE-2026-103577?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its high severity, prioritise patching exposed systems.

When was CVE-2026-103577 published?

CVE-2026-103577 was published on 2026-10-13.

CVE-2026-103577

CVE-2026-103577 is a high-severity vulnerability with a CVSS 3.x base score of 7.5. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-453.

Key facts

Severity: High (CVSS 3.x base score 7.5)
EPSS exploit prediction: 1% (43rd percentile)
Actively exploited: Not listed in CISA KEV
Weakness: CWE-453
Published: 2026-10-13
Last modified: 2026-10-13

Description

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

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.
How severe is CVE-2026-103577?: CVE-2026-103577 has a CVSS 3.x base score of 7.5, rated high severity. It is exploitable over network with high attack complexity, requires no privileges and no user interaction. Impact on confidentiality is none, integrity low, and availability high.
Is CVE-2026-103577 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (43rd percentile), an estimate of the probability of exploitation in the next 30 days.
How do I fix CVE-2026-103577?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its high severity, prioritise patching exposed systems.
When was CVE-2026-103577 published?: CVE-2026-103577 was published on 2026-10-13.

References

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

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