CVE-2026-42899: ASP.NET Core Denial of Service Vulnerability

Severity: high (CVSS 7.5 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 2.4% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2026-05-12 · updated 2026-10-26
Weakness: CWE-835

Description

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

Affected products

Microsoft .NET: from 8.0.0 before 8.0.27; from 9.0.0 before 9.0.16; from 10.0.0 before 10.0.8 — fixed in 8.0.27, 9.0.16, 10.0.8
Microsoft .NET: from 10.0.0 before 10.0.8 — fixed in 10.0.8
Microsoft .NET 8.0: from 8.0.0 before 8.0.27 — fixed in 8.0.27
Microsoft .NET 9.0: from 9.0.0 before 9.0.16 — fixed in 9.0.16

How to fix

Upgrade to a fixed version: Microsoft .NET 8.0.27, 9.0.16, 10.0.8; Microsoft .NET 10.0.8; Microsoft .NET 8.0 8.0.27; Microsoft .NET 9.0 9.0.16. Check the vendor advisory for mitigations.

References

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