CVE-2026-62815 is a critical-severity (CVSS 9.8) Use After Free vulnerability in Microsoft.Native.Quic.MsQuic.OpenSSL. A fix is available for Microsoft.Native.Quic.MsQuic.OpenSSL — see the affected versions and patch details below.
Microsoft QUIC: Remote Code Execution Vulnerability
Exploitation Status
No confirmed exploitation observed yet
- CISA assesses this as automatable — exploitation doesn’t require manual, per-target effort, which raises the odds of mass scanning and opportunistic attacks.
- A successful exploit gives an attacker total control of the affected component, not partial access.
- CISA’s own triage has not observed active exploitation or public proof-of-concept code for this CVE as of its last assessment.
Exploitation and automatability from CISA’s SSVC triage for CVE-2026-62815.
EPSS Exploitation Probability
Probability of exploitation in the next 30 days, from FIRST.org EPSS.
How urgent is this, really
Where this sits among everything scored
Real-World Exposure
Microsoft.Native.Quic.MsQuic.OpenSSL.NETMicrosoft.Native.Quic.MsQuic.Schannel.NETMicrosoft.Native.Quic.MsQuic.OpenSSL.NETMicrosoft.Native.Quic.MsQuic.SchannelReal-time download stats are indexed for npm and PyPI packages. This vulnerability affects NuGet packages — download data is not available via public APIs for these ecosystems.
Description
Summary
Use after free in Microsoft QUIC allows an unauthorized attacker to execute code over a network.
Details
New network path creations and removals triggered by incoming packets can lead to a pointer invalidation.
Patches
- Guard path promotion e0f55b5
Impact
An unauthenticated attacker could exploit this vulnerability by sending a specially crafted packet to an affected service over the network. Successful exploitation could allow the attacker to execute code on the target system. No authentication or user interaction is required.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| .NETNuGet | Microsoft.Native.Quic.MsQuic.OpenSSL | ≥ 2.5.3&&< 2.5.10 | 2.5.10dotnet add package Microsoft.Native.Quic.MsQuic.OpenSSL --version 2.5.10 |
| .NETNuGet | Microsoft.Native.Quic.MsQuic.Schannel | ≥ 2.5.3&&< 2.5.10 | 2.5.10dotnet add package Microsoft.Native.Quic.MsQuic.Schannel --version 2.5.10 |
| .NETNuGet | Microsoft.Native.Quic.MsQuic.OpenSSL | all versions | 2.4.19dotnet add package Microsoft.Native.Quic.MsQuic.OpenSSL --version 2.4.19 |
| .NETNuGet | Microsoft.Native.Quic.MsQuic.Schannel | all versions | 2.4.19dotnet add package Microsoft.Native.Quic.MsQuic.Schannel --version 2.4.19 |
Affected Products
windows 11 23h2microsoftwindows 11 24h2microsoftwindows 11 25h2microsoftwindows 11 26h1microsoftwindows server 2022microsoftwindows server 2025microsoftDetection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for Microsoft.Native.Quic.MsQuic.OpenSSL, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update Microsoft.Native.Quic.MsQuic.OpenSSL to 2.5.10 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-62815 is resolved across your whole dependency graph.
Workarounds
Stop feeding it untrusted input: reject or quarantine files and payloads from unverified sources until you can upgrade, restrict accepted formats to the ones you actually need, and run the parsing or decoding step in a least-privileged sandbox or short-lived worker so a crash or corrupted read cannot reach the rest of the process.
Frequently Asked Questions
Is CVE-2026-62815 in your dependencies?
Find it across NuGet, including transitive dependencies.