CISA adds actively exploited flaw in .NET, Visual Studio to its Known Exploited Vulnerabilities catalog

CVE-2023-38180 is a denial-of-service vulnerability in Microsoft .NET and Visual Studio 2022 caused by uncontrolled resource consumption (CWE-400). Per the CVSS vector, a remote, unauthenticated attacker can trigger it over the network with no privileges or user interaction required, causing affected applications or services to exhaust resources and become unavailable. The attacker gains only availability impact (high availability severity, no confidentiality or integrity impact), but this can take down ASP.NET Core web applications and other .NET-based services. Any organization running vulnerable .NET runtimes, ASP.NET Core applications, or Visual Studio 2022 is exposed, and Fedora also ships affected .NET packages. The flaw is being actively exploited in the wild: CISA added it to the Known Exploited Vulnerabilities catalog on 2023-08-09, it was among the two actively exploited flaws fixed in Microsoft's August 2023 Patch Tuesday, and EPSS assigns a 14.0% 30-day exploitation probability (96th percentile).

Do: Apply the August 2023 Microsoft security updates for all affected .NET, ASP.NET Core, and Visual Studio 2022 versions listed in Microsoft's advisory, and install the updated .NET packages on Fedora; because this flaw is in CISA's KEV catalog, the required action is to apply vendor mitigations or discontinue use of the product if mitigations are unavailable. After updating, rebuild or restart .NET applications so they run on the patched runtime, and monitor internet-facing .NET services for signs of resource-exhaustion denial-of-service. No public proof-of-concept is known, but active exploitation has been reported, so patching should be treated as urgent.