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.NET
.NET NuGet
Not in CISA KEV
HIGH severity

CVE-2023-21538

HIGH

CVE-2023-21538 is a high-severity (CVSS 7.5) Deserialization of Untrusted Data vulnerability in Microsoft.NETCore.App.Runtime.linux-arm. O3 Security confirms whether CVE-2023-21538 is actually reachable in your code before you act, and blocks exploitation at runtime until you patch.

.NET Denial of Service Vulnerability

Also known asBIT-dotnet-2023-21538BIT-dotnet-sdk-2023-21538BIT-powershell-2023-21538GHSA-8f7f-vqg5-jrv9
Published
Jan 10, 2023
Updated
Jul 8, 2026
Affected
12 pkgs
Patched
12 / 12
Exploits
None indexed
Exploitation data as of Jul 8, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

Real-World Exposure

12 pkgs affected
.NETMicrosoft.NETCore.App.Runtime.linux-arm.NETMicrosoft.NETCore.App.Runtime.linux-arm64.NETMicrosoft.NETCore.App.Runtime.linux-musl-arm.NETMicrosoft.NETCore.App.Runtime.linux-musl-arm64.NETMicrosoft.NETCore.App.Runtime.linux-musl-x64.NETMicrosoft.NETCore.App.Runtime.linux-x64.NETMicrosoft.NETCore.App.Runtime.osx-arm64.NETMicrosoft.NETCore.App.Runtime.osx-x64+4 more

Real-time download stats are indexed for npm and PyPI packages. This vulnerability affects NuGet packages — download data is not available via public APIs for these ecosystems.

Description

.NET Denial of Service Vulnerability

Affected Packages

12 total 12 fixed
EcosystemPackageVulnerable rangeFix
.NETNuGetMicrosoft.NETCore.App.Runtime.linux-arm6.0.0&&< 6.0.136.0.13
.NETNuGetMicrosoft.NETCore.App.Runtime.linux-arm646.0.0&&< 6.0.136.0.13
.NETNuGetMicrosoft.NETCore.App.Runtime.linux-musl-arm6.0.0&&< 6.0.136.0.13
.NETNuGetMicrosoft.NETCore.App.Runtime.linux-musl-arm646.0.0&&< 6.0.136.0.13
.NETNuGetMicrosoft.NETCore.App.Runtime.linux-musl-x646.0.0&&< 6.0.136.0.13
.NETNuGetMicrosoft.NETCore.App.Runtime.linux-x646.0.0&&< 6.0.136.0.13

Detection & mitigation playbook

Open-source dependency
  1. Detect

    Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for Microsoft.NETCore.App.Runtime.linux-arm. O3's reachability analysis confirms whether the vulnerable code path is actually invoked in your application, so you act on real exposure instead of every transitive match.

  2. Fix

    Update Microsoft.NETCore.App.Runtime.linux-arm to 6.0.13 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2023-21538 is resolved across your whole dependency graph.

  3. Workarounds

    If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.

  4. How O3 protects you

    O3 pinpoints whether CVE-2023-21538 is reachable in your code and exactly where to fix it, then blocks exploitation in production at runtime until the patched version is deployed.

Tailored to CVE-2023-21538. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.

Frequently Asked Questions

.NET Denial of Service Vulnerability
O3 Security · Impact-Aware SCA

Is CVE-2023-21538 in your dependencies?

O3 detects CVE-2023-21538 across NuGet dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.