CVE-2026-62815Network attack vector

Unauthenticated code execution via stale path promotion

Published Aug 11, 2026 · Updated Aug 25, 2026

Use after free in Microsoft QUIC on affected Windows releases allows remote attackers to execute code through a crafted network packet. During NEW_CONNECTION_ID processing, QuicConnReplaceRetiredCids can remove and free a path, but QuicConnRecvPostProcessing later promotes the stale path without checking InUse. No authentication or user interaction is required, and successful exploitation runs code on the target system.

CVSS severity10.0
Critical
EPSS probability1.24%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Use after free in Microsoft QUIC on affected Windows releases allows remote attackers to execute code through a crafted network packet. During NEW_CONNECTION_ID processing, QuicConnReplaceRetiredCids can remove and free a path, but QuicConnRecvPostProcessing later promotes the stale path without checking InUse. No authentication or user interaction is required, and successful exploitation runs code on the target system.

The record

CVE
CVE-2026-62815
Published
Aug 11, 2026
Updated
Aug 25, 2026
Vendor
Microsoft
Product
Windows Server 2025 (Server Core installation)
Classifications
CWE-416, T1210
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Aug 11, 2026CVE publishedPublication date reported by the CVE source.
  2. Aug 25, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=10.0.26100.0 <10.0.26100.33296

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Microsoft · Windows Server 2025 (Server Core installation)version=10.0.26100.0 <10.0.26100.33296
Microsoft · Windows 11, version 25H2version=10.0.26200.0 <10.0.26200.9168
Microsoft · Windows 11, version 24H2version=10.0.26100.0 <10.0.26100.9168
Microsoft · Windows 11, version 26H1version=10.0.28000.0 <10.0.28000.2704
Microsoft · Windows 11 Version 23H2version=10.0.22631.0 <10.0.22631.7517
Microsoft · Windows Server 2022version=10.0.20348.0 <10.0.20348.5499
Microsoft · Windows Server 2025version=10.0.26100.0 <10.0.26100.33296

Published CVSS scores

9.8MicrosoftCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
10.0GitHub Advisory DatabaseCVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:H/SI:H/SA:H

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 9, 2026Sep 15, 2026
Latest reporting daySep 15, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-416Use After Free
T1210Exploitation of Remote Services

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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