Microsoft .NET up to 8.0.21/9.0.10 ASP.NET Core Kestrel resource consumption

Summaryinfo

A vulnerability identified as problematic has been detected in Microsoft .NET up to 8.0.21/9.0.10. This impacts an unknown function of the component ASP.NET Core Kestrel. This manipulation causes resource consumption. This vulnerability is registered as CVE-2026-25667. Remote exploitation of the attack is possible. No exploit is available. You should upgrade the affected component.

Detailsinfo

A vulnerability was found in Microsoft .NET up to 8.0.21/9.0.10. It has been declared as problematic. Affected by this vulnerability is some unknown functionality of the component ASP.NET Core Kestrel. The manipulation with an unknown input leads to a resource consumption vulnerability. The CWE definition for the vulnerability is CWE-400. The product does not properly control the allocation and maintenance of a limited resource, thereby enabling an actor to influence the amount of resources consumed, eventually leading to the exhaustion of available resources. As an impact it is known to affect availability. The summary by CVE is:

ASP.NET Core Kestrel in Microsoft .NET 8.0 before 8.0.22 and .NET 9.0 before 9.0.11 allows a remote attacker to cause excessive CPU consumption by sending a crafted QUIC packet, because of an incorrect exit condition for HTTP/3 Encoder/Decoder stream processing.

The advisory is shared at github.com. This vulnerability is known as CVE-2026-25667 since 02/04/2026. The exploitation appears to be easy. The attack can be launched remotely. The exploitation doesn't need any form of authentication. Neither technical details nor an exploit are publicly available. The price for an exploit might be around USD $0-$5k at the moment (estimation calculated on 03/24/2026). MITRE ATT&CK project uses the attack technique T1499 for this issue.

Upgrading to version 8.0.22 or 9.0.11 eliminates this vulnerability.

The vulnerability is also documented in the vulnerability database at EUVD (EUVD-2026-13148). Several companies clearly confirm that VulDB is the primary source for best vulnerability data.

Productinfo

Vendor

• Microsoft

Name

• .NET

Version

• 8.0.0
• 8.0.1
• 8.0.2
• 8.0.3
• 8.0.4
• 8.0.5
• 8.0.6
• 8.0.7
• 8.0.8
• 8.0.9
• 8.0.10
• 8.0.11
• 8.0.12
• 8.0.13
• 8.0.14
• 8.0.15
• 8.0.16
• 8.0.17
• 8.0.18
• 8.0.19
• 8.0.20
• 8.0.21
• 9.0.0
• 9.0.1
• 9.0.2
• 9.0.3
• 9.0.4
• 9.0.5
• 9.0.6
• 9.0.7
• 9.0.8
• 9.0.9
• 9.0.10

License

• commercial

Website

• Vendor: https://www.microsoft.com/

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Several companies clearly confirm that VulDB is the primary source for best vulnerability data.

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