CVE-2026-42899 ASP.NET Core Denial of Service Vulnerability
High 7.5
Published
Updated
Check this codebase for CVE-2026-42899 and fix it if it is affected.
What it is: CVE-2026-42899 is a high-severity denial of service vulnerability in Microsoft .Net, published on 12 May 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2026-42899 in the wild and no public exploit code.
Affected packages and fixed versions:
- Microsoft.AspNetCore.App.Runtime.linux-arm (NuGet): affected from 10.0.0; fixed in 10.0.8
- Microsoft.AspNetCore.App.Runtime.linux-arm (NuGet): affected from 10.0.0; fixed in 10.0.8
- Microsoft.AspNetCore.App.Runtime.linux-arm (NuGet): affected from 8.0.0; fixed in 8.0.27
- Microsoft.AspNetCore.App.Runtime.linux-arm (NuGet): affected from 8.0.0; fixed in 8.0.27
- Microsoft.AspNetCore.App.Runtime.linux-arm (NuGet): affected from 9.0.0; fixed in 9.0.16
- Microsoft.AspNetCore.App.Runtime.linux-arm (NuGet): affected from 9.0.0; fixed in 9.0.16
- dotnet (Bitnami): affected from 8.0.0; fixed in 8.0.27, 9.0.16, 10.0.8
- dotnet-sdk (Bitnami): affected from 8.0.0; fixed in 8.0.27, 9.0.16, 10.0.8
- Microsoft.AspNetCore.App.Runtime.linux-arm64 (NuGet): affected from 10.0.0; fixed in 10.0.8
- Microsoft.AspNetCore.App.Runtime.linux-arm64 (NuGet): affected from 10.0.0; fixed in 10.0.8
- Microsoft.AspNetCore.App.Runtime.linux-arm64 (NuGet): affected from 8.0.0; fixed in 8.0.27
- Microsoft.AspNetCore.App.Runtime.linux-arm64 (NuGet): affected from 8.0.0; fixed in 8.0.27
Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.
Reference: https://insights.sbomify.com/CVE-2026-42899/ (Markdown: https://insights.sbomify.com/CVE-2026-42899/index.md)
An unauthorized attacker can cause a denial of service in ASP.NET Core via an infinite loop, requiring a patch.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-42899?
CVE-2026-42899 is a high-severity denial of service vulnerability in Microsoft .Net, published on 12 May 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official description
Loop with unreachable exit condition ('infinite loop') in ASP.NET Core allows an unauthorized attacker to deny service over a network.
Weakness: CWE-835
Which versions are affected by CVE-2026-42899?
40 open source packages ship an affected version, including Microsoft.AspNetCore.App.Runtime.linux-arm, dotnet and dotnet-sdk. It affects 1 product.
| Package | Affected | Fixed in |
|---|---|---|
Microsoft.AspNetCore.App.Runtime.linux-arm NuGet | From 10.0.0 | 10.0.8 |
Microsoft.AspNetCore.App.Runtime.linux-arm NuGet | From 10.0.0 | 10.0.8 |
Microsoft.AspNetCore.App.Runtime.linux-arm NuGet | From 8.0.0 | 8.0.27 |
Microsoft.AspNetCore.App.Runtime.linux-arm NuGet | From 8.0.0 | 8.0.27 |
Microsoft.AspNetCore.App.Runtime.linux-arm NuGet | From 9.0.0 | 9.0.16 |
Microsoft.AspNetCore.App.Runtime.linux-arm NuGet | From 9.0.0 | 9.0.16 |
34 more packages
dotnet Bitnami | From 8.0.0 | 8.0.27, 9.0.16, 10.0.8 |
dotnet-sdk Bitnami | From 8.0.0 | 8.0.27, 9.0.16, 10.0.8 |
Microsoft.AspNetCore.App.Runtime.linux-arm64 NuGet | From 10.0.0 | 10.0.8 |
Microsoft.AspNetCore.App.Runtime.linux-arm64 NuGet | From 10.0.0 | 10.0.8 |
Microsoft.AspNetCore.App.Runtime.linux-arm64 NuGet | From 8.0.0 | 8.0.27 |
Microsoft.AspNetCore.App.Runtime.linux-arm64 NuGet | From 8.0.0 | 8.0.27 |
Microsoft.AspNetCore.App.Runtime.linux-arm64 NuGet | From 9.0.0 | 9.0.16 |
Microsoft.AspNetCore.App.Runtime.linux-arm64 NuGet | From 9.0.0 | 9.0.16 |
Microsoft.AspNetCore.App.Runtime.linux-musl-arm NuGet | From 10.0.0 | 10.0.8 |
Microsoft.AspNetCore.App.Runtime.linux-musl-arm NuGet | From 10.0.0 | 10.0.8 |
Microsoft.AspNetCore.App.Runtime.linux-musl-arm NuGet | From 8.0.0 | 8.0.27 |
Microsoft.AspNetCore.App.Runtime.linux-musl-arm NuGet | From 8.0.0 | 8.0.27 |
Microsoft.AspNetCore.App.Runtime.linux-musl-arm NuGet | From 9.0.0 | 9.0.16 |
Microsoft.AspNetCore.App.Runtime.linux-musl-arm NuGet | From 9.0.0 | 9.0.16 |
Microsoft.AspNetCore.App.Runtime.linux-musl-arm64 NuGet | From 10.0.0 | 10.0.8 |
Microsoft.AspNetCore.App.Runtime.linux-musl-arm64 NuGet | From 10.0.0 | 10.0.8 |
Microsoft.AspNetCore.App.Runtime.linux-musl-arm64 NuGet | From 8.0.0 | 8.0.27 |
Microsoft.AspNetCore.App.Runtime.linux-musl-arm64 NuGet | From 8.0.0 | 8.0.27 |
Microsoft.AspNetCore.App.Runtime.linux-musl-arm64 NuGet | From 9.0.0 | 9.0.16 |
Microsoft.AspNetCore.App.Runtime.linux-musl-arm64 NuGet | From 9.0.0 | 9.0.16 |
Microsoft.AspNetCore.App.Runtime.linux-musl-x64 NuGet | From 10.0.0 | 10.0.8 |
Microsoft.AspNetCore.App.Runtime.linux-musl-x64 NuGet | From 10.0.0 | 10.0.8 |
Microsoft.AspNetCore.App.Runtime.linux-musl-x64 NuGet | From 8.0.0 | 8.0.27 |
Microsoft.AspNetCore.App.Runtime.linux-musl-x64 NuGet | From 8.0.0 | 8.0.27 |
Microsoft.AspNetCore.App.Runtime.linux-musl-x64 NuGet | From 9.0.0 | 9.0.16 |
Microsoft.AspNetCore.App.Runtime.linux-musl-x64 NuGet | From 9.0.0 | 9.0.16 |
Microsoft.AspNetCore.App.Runtime.linux-x64 NuGet | From 10.0.0 | 10.0.8 |
Microsoft.AspNetCore.App.Runtime.linux-x64 NuGet | From 10.0.0 | 10.0.8 |
Microsoft.AspNetCore.App.Runtime.linux-x64 NuGet | From 8.0.0 | 8.0.27 |
Microsoft.AspNetCore.App.Runtime.linux-x64 NuGet | From 8.0.0 | 8.0.27 |
Microsoft.AspNetCore.App.Runtime.linux-x64 NuGet | From 9.0.0 | 9.0.16 |
Microsoft.AspNetCore.App.Runtime.linux-x64 NuGet | From 9.0.0 | 9.0.16 |
Microsoft.AspNetCore.App.Runtime.osx-arm64 NuGet | From 10.0.0 | 10.0.8 |
Microsoft.AspNetCore.App.Runtime.osx-arm64 NuGet | From 10.0.0 | 10.0.8 |
Products include Microsoft .Net.
How do I fix CVE-2026-42899?
Upgrade Microsoft.AspNetCore.App.Runtime.linux-arm to a fixed version for your release line: 10.0.8, 8.0.27 or 9.0.16.
Upgrade, then put limits on request size, rate and nesting depth so one client cannot exhaust the service. More about Denial of service.
Is CVE-2026-42899 being exploited?
There is no known exploitation of CVE-2026-42899 in the wild and no public exploit code.
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Sources
Also known as ALSA-2026:21294, ALSA-2026:21295, ALSA-2026:21296, ALSA-2026:21297, ALSA-2026:21754, ALSA-2026:22145 and 23 more.