CVE-2026-62898

Use after free in Microsoft QUIC allows an unauthorized attacker to disclose information over a network.

Use after free in Microsoft QUIC allows an unauthorized attacker to disclose information over a network.

Executive summary

Microsoft is releasing this security advisory to provide information about a vulnerability in Microsoft QUIC. This advisory also provides guidance on what developers can do to update their applications to remove this vulnerability.

A use after free in Microsoft QUIC allows an unauthorized attacker to disclose information over a network.

Announcement

Announcement for this issue can be found at https://github.com/dotnet/announcements/issues/426

CVSS Details

• Version: 3.1
• Severity: High
• Score: 7.5
• Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N/E:U/RL:O/RC:C
• Weakness: CWE-416: Use After Free

Affected Platforms

• Platforms: Windows
• Architectures: All

<a name="affected-packages"></a>Affected Packages

The vulnerability affects any Microsoft .NET project if it uses any of affected package versions listed below

<a name=".NET 10"></a>.NET 10

Package name | Affected version | Patched version ------------ | ---------------- | ------------------------- Microsoft.NETCore.App.Runtime.win-arm64 | >= 10.0.0, <= 10.0.10 | 10.0.11 Microsoft.NETCore.App.Runtime.win-x64 | >= 10.0.0, <= 10.0.10 | 10.0.11 Microsoft.NETCore.App.Runtime.win-x86 | >= 10.0.0, <= 10.0.10 | 10.0.11

<a name=".NET 9"></a>.NET 9

Package name | Affected version | Patched version ------------ | ---------------- | ------------------------- Microsoft.NETCore.App.Runtime.win-arm64 | >= 9.0.0, <= 9.0.18 | 9.0.19 Microsoft.NETCore.App.Runtime.win-x64 | >= 9.0.0, <= 9.0.18 | 9.0.19 Microsoft.NETCore.App.Runtime.win-x86 | >= 9.0.0, <= 9.0.18 | 9.0.19

<a name=".NET 8"></a>.NET 8

Package name | Affected version | Patched version ------------ | ---------------- | ------------------------- Microsoft.NETCore.App.Runtime.win-arm64 | >= 8.0.0, <= 8.0.29 | 8.0.30 Microsoft.NETCore.App.Runtime.win-x64 | >= 8.0.0, <= 8.0.29 | 8.0.30 Microsoft.NETCore.App.Runtime.win-x86 | >= 8.0.0, <= 8.0.29 | 8.0.30

Advisory FAQ

<a name="how-affected"></a>How do I know if I am affected?

If using a package listed in affected packages, an application is exposed to the vulnerability.

<a name="how-fix"></a>How do I fix the issue?

1. To fix the issue please install the latest version of .NET. If an application has installed one or more .NET SDKs through Visual Studio, Visual Studio will prompt a user to update Visual Studio, which will also update their .NET SDKs.
2. If an application references the vulnerable package, update the package reference to the patched version. Users can list the versions they have installed by running the dotnet --info command.

Once users have installed the updated runtime or SDK, they need to restart their apps for the update to take effect.

Additionally, if users have deployed self-contained applications targeting any of the impacted versions, these applications are also vulnerable and must be recompiled and redeployed.

Other Information

Reporting Security Issues

If users have found a potential security issue in a supported version of .NET, please report it to the Microsoft Security Response Center (MSRC) via the MSRC Researcher Portal. Further…

Use after free in Microsoft QUIC allows an unauthorized attacker to disclose information over a network.

Use after free in Microsoft QUIC allows an unauthorized attacker to disclose information over a network.