CVE-2026-62815: Microsoft QUIC Remote Code Execution Vulnerability

CSIRTS triage

What

Use-after-free vulnerability enables remote code execution without authentication.

Who is affected

Any system running Microsoft QUIC over a network.

Urgency

Critical severity (CVSS 9.8) with network-based RCE; patch immediately regardless of exploitation status.

Action

Prioritize patching or disable Microsoft QUIC if possible pending immediate security update.

AI-assisted analysis generated from the source advisory — verify against the original.

Details

Source

Microsoft Security Response Center (INTL · vendor-psirt · site)

Severity

critical — CVSS 9.8

Published

2026-08-11

Exploitation

Not in CISA KEV at last sync

Original advisory: https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-62815

Exploitation outlook

EPSS (FIRST.org) estimates each CVE’s probability of exploitation in the next 30 days — here is the CSIRTS.com read on those numbers.

• Low exploitation riskCVE-2026-628150.92% 30-day exploitation probability — currently an unlikely target, but scores change as exploit code circulates. Riskier than 57% of all EPSS-scored CVEs.

Referenced CVEs

Same CVEs, other sources

How other CERTs, PSIRTs and databases cover the vulnerabilities in this advisory.

• unknownexploitedNCSC-2026-0284 [1.00] [M/H] Vulnerabilities patched in Microsoft Windowsncsc-nl
• criticalCVE-2026-62815: Use after free in Microsoft QUIC allows an unauthorized attacker to execute code over a networ…nvd

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