Ubuntu 26.04 LTS Dotnet Critical Denial of Service Threat USN-8420-1

ubuntu

June 11, 2026

Several security issues were fixed in .NET.

Summary

Several security issues were fixed in .NET.

Software Description:

- dotnet10: .NET CLI tools and runtime

- dotnet8: .NET CLI tools and runtime

- dotnet9: .NET CLI tools and runtime

Details:

It was discovered that .NET did not properly handle link resolution before

file access. A local attacker could use this issue to perform unauthorized

file tampering and write arbitrary files outside of the intended extraction

directory. (CVE-2026-45491)

It was discovered that .NET did not properly handle deeply-nested

MessagePack arrays. An attacker could use this to cause .NET to consume

excessive resources, resulting in a denial of service. (CVE-2026-45591)

Topics Covered

security advisory moderate denial of service Ubuntu dotnet file tampering

Update Instructions

The problem can be corrected by updating your system to the following
package versions:

Ubuntu 26.04 LTS
  aspnetcore-runtime-10.0         10.0.9-0ubuntu1~26.04.1
  dotnet-host-10.0                10.0.9-0ubuntu1~26.04.1
  dotnet-hostfxr-10.0             10.0.9-0ubuntu1~26.04.1
  dotnet-runtime-10.0             10.0.9-0ubuntu1~26.04.1
  dotnet-sdk-10.0                 10.0.109-0ubuntu1~26.04.1
  dotnet-sdk-aot-10.0             10.0.109-0ubuntu1~26.04.1
  dotnet-sdk-dbg-10.0             10.0.109-0ubuntu1~26.04.1
  dotnet10                        10.0.109-10.0.9-0ubuntu1~26.04.1

Ubuntu 25.10
  aspnetcore-runtime-10.0         10.0.9-0ubuntu1~25.10.1
  aspnetcore-runtime-8.0          8.0.28-0ubuntu1~25.10.1
  aspnetcore-runtime-9.0          9.0.17-0ubuntu1~25.10.1
  dotnet-host-10.0                10.0.9-0ubuntu1~25.10.1
  dotnet-host-8.0                 8.0.28-0ubuntu1~25.10.1
  dotnet-host-9.0                 9.0.17-0ubuntu1~25.10.1
  dotnet-hostfxr-10.0             10.0.9-0ubuntu1~25.10.1
  dotnet-hostfxr-8.0              8.0.28-0ubuntu1~25.10.1
  dotnet-hostfxr-9.0              9.0.17-0ubuntu1~25.10.1
  dotnet-runtime-10.0             10.0.9-0ubuntu1~25.10.1
  dotnet-runtime-8.0              8.0.28-0ubuntu1~25.10.1
  dotnet-runtime-9.0              9.0.17-0ubuntu1~25.10.1
  dotnet-sdk-10.0                 10.0.109-0ubuntu1~25.10.1
  dotnet-sdk-8.0                  8.0.128-0ubuntu1~25.10.1
  dotnet-sdk-9.0                  9.0.118-0ubuntu1~25.10.1
  dotnet-sdk-aot-10.0             10.0.109-0ubuntu1~25.10.1
  dotnet-sdk-aot-9.0              9.0.118-0ubuntu1~25.10.1
  dotnet-sdk-dbg-10.0             10.0.109-0ubuntu1~25.10.1
  dotnet-sdk-dbg-9.0              9.0.118-0ubuntu1~25.10.1
  dotnet10                        10.0.109-10.0.9-0ubuntu1~25.10.1
  dotnet8                         8.0.128-8.0.28-0ubuntu1~25.10.1
  dotnet9                         9.0.118-9.0.17-0ubuntu1~25.10.1

Ubuntu 24.04 LTS
  aspnetcore-runtime-10.0         10.0.9-0ubuntu1~24.04.1
  aspnetcore-runtime-8.0          8.0.28-0ubuntu1~24.04.1
  dotnet-host-10.0                10.0.9-0ubuntu1~24.04.1
  dotnet-host-8.0                 8.0.28-0ubuntu1~24.04.1
  dotnet-hostfxr-10.0             10.0.9-0ubuntu1~24.04.1
  dotnet-hostfxr-8.0              8.0.28-0ubuntu1~24.04.1
  dotnet-runtime-10.0             10.0.9-0ubuntu1~24.04.1
  dotnet-runtime-8.0              8.0.28-0ubuntu1~24.04.1
  dotnet-sdk-10.0                 10.0.109-0ubuntu1~24.04.1
  dotnet-sdk-8.0                  8.0.128-0ubuntu1~24.04.1
  dotnet-sdk-aot-10.0             10.0.109-0ubuntu1~24.04.1
  dotnet-sdk-dbg-10.0             10.0.109-0ubuntu1~24.04.1
  dotnet10                        10.0.109-10.0.9-0ubuntu1~24.04.1
  dotnet8                         8.0.128-8.0.28-0ubuntu1~24.04.1

Ubuntu 22.04 LTS
  aspnetcore-runtime-8.0          8.0.28-0ubuntu1~22.04.1
  dotnet-host-8.0                 8.0.28-0ubuntu1~22.04.1
  dotnet-hostfxr-8.0              8.0.28-0ubuntu1~22.04.1
  dotnet-runtime-8.0              8.0.28-0ubuntu1~22.04.1
  dotnet-sdk-8.0                  8.0.128-0ubuntu1~22.04.1
  dotnet8                         8.0.128-8.0.28-0ubuntu1~22.04.1

In general, a standard system update will make all the necessary changes.