CVE-2026-42899

Executive Summary:

Microsoft is releasing this security advisory to provide information about a vulnerability in .NET 8.0, .NET 9.0, and .NET 10.0. This advisory also provides guidance on what developers can do to update their applications to remove this vulnerability.

Loop with unreachable exit condition ('infinite loop') in ASP.NET Core allows an unauthorized attacker to deny service over a network.

Announcement

Announcement for this issue can be found at https://github.com/dotnet/announcements/issues/397

CVSS Details

• Version: 3.1
• Severity:
• Score: 7.5
• Vector: AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H/E:U/RL:O/RC:C
• Weakness: CWE-835: Loop with Unreachable Exit Condition ('Infinite Loop')

Affected Platforms

• Platforms: All
• 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.AspNetCore.App.Runtime.win-arm | >= 10.0.0, <= 10.0.7 | 10.0.8 Microsoft.AspNetCore.App.Runtime.win-arm64 | >= 10.0.0, <= 10.0.7 | 10.0.8 Microsoft.AspNetCore.App.Runtime.win-x64 | >= 10.0.0, <= 10.0.7 | 10.0.8 Microsoft.AspNetCore.App.Runtime.win-x86 | >= 10.0.0, <= 10.0.7 | 10.0.8 Microsoft.AspNetCore.App.Runtime.linux-arm | >= 10.0.0, <= 10.0.7 | 10.0.8 Microsoft.AspNetCore.App.Runtime.linux-arm64 | >= 10.0.0, <= 10.0.7 | 10.0.8 Microsoft.AspNetCore.App.Runtime.linux-musl-arm | >= 10.0.0, <= 10.0.7 | 10.0.8 Microsoft.AspNetCore.App.Runtime.linux-musl-arm64 | >= 10.0.0, <= 10.0.7 | 10.0.8 Microsoft.AspNetCore.App.Runtime.linux-musl-x64 | >= 10.0.0, <= 10.0.7 | 10.0.8 Microsoft.AspNetCore.App.Runtime.linux-x64 | >= 10.0.0, <= 10.0.7 | 10.0.8 Microsoft.AspNetCore.App.Runtime.osx-arm64 | >= 10.0.0, <= 10.0.7 | 10.0.8 Microsoft.AspNetCore.App.Runtime.osx-x64 | >= 10.0.0, <= 10.0.7 | 10.0.8

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

Package name | Affected version | Patched version ------------ | ---------------- | ------------------------- Microsoft.AspNetCore.App.Runtime.win-arm | >= 9.0.0, <= 9.0.15 | 9.0.16 Microsoft.AspNetCore.App.Runtime.win-arm64 | >= 9.0.0, <= 9.0.15 | 9.0.16 Microsoft.AspNetCore.App.Runtime.win-x64 | >= 9.0.0, <= 9.0.15 | 9.0.16 Microsoft.AspNetCore.App.Runtime.win-x86 | >= 9.0.0, <= 9.0.15 | 9.0.16…

.NET is a managed-software framework. It implements a subset of the .NET framework APIs and several new APIs, and it includes a CLR implementation.

New versions of .NET that address a security vulnerability are now available. The updated versions are .NET SDK 8.0.127 and .NET Runtime 8.0.27.Security Fix(es):

• serialize-javascript: serialize-javascript: Denial of Service via specially crafted array-like object serialization (CVE-2026-34043)

• dotnet: .NET: infinite loop allows an attacker to cause a denial of service (CVE-2026-42899)

For more details about the security issue(s), including the impact, a CVSS score, acknowledgments, and other related information, refer to the CVE page(s) listed in the References section.

.NET is a managed-software framework. It implements a subset of the .NET framework APIs and several new APIs, and it includes a CLR implementation.

New versions of .NET that address a security vulnerability are now available. The updated versions are .NET SDK 8.0.127 and .NET Runtime 8.0.27.Security Fix(es):

• serialize-javascript: serialize-javascript: Denial of Service via specially crafted array-like object serialization (CVE-2026-34043)

• dotnet: .NET: infinite loop allows an attacker to cause a denial of service (CVE-2026-42899)

For more details about the security issue(s), including the impact, a CVSS score, acknowledgments, and other related information, refer to the CVE page(s) listed in the References section.

.NET is a managed-software framework. It implements a subset of the .NET framework APIs and several new APIs, and it includes a CLR implementation.

New versions of .NET that address a security vulnerability are now available. The updated versions are .NET SDK 8.0.127 and .NET Runtime 8.0.27.Security Fix(es):

• serialize-javascript: serialize-javascript: Denial of Service via specially crafted array-like object serialization (CVE-2026-34043)

• dotnet: .NET: infinite loop allows an attacker to cause a denial of service (CVE-2026-42899)

For more details about the security issue(s), including the impact, a CVSS score, acknowledgments, and other related information, refer to the CVE page(s) listed in the References section.

.NET is a managed-software framework. It implements a subset of the .NET framework APIs and several new APIs, and it includes a CLR implementation.

New versions of .NET that address a security vulnerability are now available. The updated versions are .NET SDK 9.0.117 and .NET Runtime 9.0.16.Security Fix(es):

• dotnet: .NET: infinite loop allows an attacker to cause a denial of service (CVE-2026-42899)

For more details about the security issue(s), including the impact, a CVSS score, acknowledgments, and other related information, refer to the CVE page(s) listed in the References section.

.NET is a managed-software framework. It implements a subset of the .NET framework APIs and several new APIs, and it includes a CLR implementation.

New versions of .NET that address a security vulnerability are now available. The updated versions are .NET SDK 10.0.108 and .NET Runtime 10.0.8.Security Fix(es):

• dotnet: .NET: infinite loop allows an attacker to cause a denial of service (CVE-2026-42899)

For more details about the security issue(s), including the impact, a CVSS score, acknowledgments, and other related information, refer to the CVE page(s) listed in the References section.

.NET is a managed-software framework. It implements a subset of the .NET framework APIs and several new APIs, and it includes a CLR implementation.

New versions of .NET that address a security vulnerability are now available. The updated versions are .NET SDK 9.0.117 and .NET Runtime 9.0.16.Security Fix(es):

• dotnet: .NET: infinite loop allows an attacker to cause a denial of service (CVE-2026-42899)

For more details about the security issue(s), including the impact, a CVSS score, acknowledgments, and other related information, refer to the CVE page(s) listed in the References section.

.NET is a managed-software framework. It implements a subset of the .NET framework APIs and several new APIs, and it includes a CLR implementation.

New versions of .NET that address a security vulnerability are now available. The updated versions are .NET SDK 10.0.108 and .NET Runtime 10.0.8.Security Fix(es):

• dotnet: .NET: infinite loop allows an attacker to cause a denial of service (CVE-2026-42899)

For more details about the security issue(s), including the impact, a CVSS score, acknowledgments, and other related information, refer to the CVE page(s) listed in the References section.

.NET is a managed-software framework. It implements a subset of the .NET framework APIs and several new APIs, and it includes a CLR implementation.

New versions of .NET that address a security vulnerability are now available. The updated versions are .NET SDK 9.0.117 and .NET Runtime 9.0.16.Security Fix(es):

• dotnet: .NET: infinite loop allows an attacker to cause a denial of service (CVE-2026-42899)

For more details about the security issue(s), including the impact, a CVSS score, acknowledgments, and other related information, refer to the CVE page(s) listed in the References section.

.NET is a managed-software framework. It implements a subset of the .NET framework APIs and several new APIs, and it includes a CLR implementation.

New versions of .NET that address a security vulnerability are now available. The updated versions are .NET SDK 10.0.108 and .NET Runtime 10.0.8.Security Fix(es):

• dotnet: .NET: infinite loop allows an attacker to cause a denial of service (CVE-2026-42899)

For more details about the security issue(s), including the impact, a CVSS score, acknowledgments, and other related information, refer to the CVE page(s) listed in the References section.

Loop with unreachable exit condition ('infinite loop') in ASP.NET Core allows an unauthorized attacker to deny service over a network.

.NET is a managed-software framework. It implements a subset of the .NET framework APIs and several new APIs, and it includes a CLR implementation.

New versions of .NET that address a security vulnerability are now available. The updated versions are .NET SDK 8.0.127 and .NET Runtime 8.0.27.Security Fix(es):

• serialize-javascript: serialize-javascript: Denial of Service via specially crafted array-like object serialization (CVE-2026-34043)
• dotnet: .NET: infinite loop allows an attacker to cause a denial of service (CVE-2026-42899)

For more details about the security issue(s), including the impact, a CVSS score, acknowledgments, and other related information, refer to the CVE page(s) listed in the References section.

.NET is a managed-software framework. It implements a subset of the .NET framework APIs and several new APIs, and it includes a CLR implementation.

New versions of .NET that address a security vulnerability are now available. The updated versions are .NET SDK 8.0.127 and .NET Runtime 8.0.27.Security Fix(es):

• serialize-javascript: serialize-javascript: Denial of Service via specially crafted array-like object serialization (CVE-2026-34043)
• dotnet: .NET: infinite loop allows an attacker to cause a denial of service (CVE-2026-42899)

For more details about the security issue(s), including the impact, a CVSS score, acknowledgments, and other related information, refer to the CVE page(s) listed in the References section.

.NET is a managed-software framework. It implements a subset of the .NET framework APIs and several new APIs, and it includes a CLR implementation.

New versions of .NET that address a security vulnerability are now available. The updated versions are .NET SDK 8.0.127 and .NET Runtime 8.0.27.Security Fix(es):

• serialize-javascript: serialize-javascript: Denial of Service via specially crafted array-like object serialization (CVE-2026-34043)
• dotnet: .NET: infinite loop allows an attacker to cause a denial of service (CVE-2026-42899)

For more details about the security issue(s), including the impact, a CVSS score, acknowledgments, and other related information, refer to the CVE page(s) listed in the References section.

.NET is a managed-software framework. It implements a subset of the .NET framework APIs and several new APIs, and it includes a CLR implementation.

New versions of .NET that address a security vulnerability are now available. The updated versions are .NET SDK 9.0.117 and .NET Runtime 9.0.16.Security Fix(es):

• dotnet: .NET: infinite loop allows an attacker to cause a denial of service (CVE-2026-42899)

For more details about the security issue(s), including the impact, a CVSS score, acknowledgments, and other related information, refer to the CVE page(s) listed in the References section.

.NET is a managed-software framework. It implements a subset of the .NET framework APIs and several new APIs, and it includes a CLR implementation.

New versions of .NET that address a security vulnerability are now available. The updated versions are .NET SDK 10.0.108 and .NET Runtime 10.0.8.Security Fix(es):

• dotnet: .NET: infinite loop allows an attacker to cause a denial of service (CVE-2026-42899)

For more details about the security issue(s), including the impact, a CVSS score, acknowledgments, and other related information, refer to the CVE page(s) listed in the References section.

.NET is a managed-software framework. It implements a subset of the .NET framework APIs and several new APIs, and it includes a CLR implementation.

New versions of .NET that address a security vulnerability are now available. The updated versions are .NET SDK 9.0.117 and .NET Runtime 9.0.16.Security Fix(es):

• dotnet: .NET: infinite loop allows an attacker to cause a denial of service (CVE-2026-42899)

For more details about the security issue(s), including the impact, a CVSS score, acknowledgments, and other related information, refer to the CVE page(s) listed in the References section.

.NET is a managed-software framework. It implements a subset of the .NET framework APIs and several new APIs, and it includes a CLR implementation.

New versions of .NET that address a security vulnerability are now available. The updated versions are .NET SDK 10.0.108 and .NET Runtime 10.0.8.Security Fix(es):

• dotnet: .NET: infinite loop allows an attacker to cause a denial of service (CVE-2026-42899)

For more details about the security issue(s), including the impact, a CVSS score, acknowledgments, and other related information, refer to the CVE page(s) listed in the References section.

.NET is a managed-software framework. It implements a subset of the .NET framework APIs and several new APIs, and it includes a CLR implementation.

New versions of .NET that address a security vulnerability are now available. The updated versions are .NET SDK 9.0.117 and .NET Runtime 9.0.16.Security Fix(es):

• dotnet: .NET: infinite loop allows an attacker to cause a denial of service (CVE-2026-42899)

For more details about the security issue(s), including the impact, a CVSS score, acknowledgments, and other related information, refer to the CVE page(s) listed in the References section.

.NET is a managed-software framework. It implements a subset of the .NET framework APIs and several new APIs, and it includes a CLR implementation.

New versions of .NET that address a security vulnerability are now available. The updated versions are .NET SDK 10.0.108 and .NET Runtime 10.0.8.Security Fix(es):

• dotnet: .NET: infinite loop allows an attacker to cause a denial of service (CVE-2026-42899)

For more details about the security issue(s), including the impact, a CVSS score, acknowledgments, and other related information, refer to the CVE page(s) listed in the References section.

Loop with unreachable exit condition ('infinite loop') in ASP.NET Core allows an unauthorized attacker to deny service over a network.

Loop with unreachable exit condition ('infinite loop') in ASP.NET Core allows an unauthorized attacker to deny service over a network.

Muhammad Abdul Rehman discovered that .NET incorrectly handled certain network requests, leading to a loop with an unreachable exit condition. A remote attacker could possibly use this issue to consume excessive resources, resulting in a denial of service.