CVE-2026-42899: Loop with unreachable exit condition ('infinite loop') in ASP.NET Core allows an unauthorized attacker to deny

Q: How do I fix CVE-2026-42899?

.net: upgrade to 8.0.27, 9.0.16, 10.0.8. Exact commands for each OS are on this page.

Q: Is CVE-2026-42899 being exploited?

CVE-2026-42899 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

Q: What does CVE-2026-42899 affect?

CVE-2026-42899 affects .net. Severity is high (CVSS 7.5). Loop with unreachable exit condition ('infinite loop') in ASP.NET Core allows an unauthorized attacker to deny service over a network.

Q: How urgent is CVE-2026-42899?

Priority 57/100. High severity; Remotely exploitable, no login, no user action; On your watchlist

This month

HIGH 7.5REMOTEWATCHLISTUPGRADE

CVE-2026-42899 is a high-severity flaw (CVSS 7.5) affecting .net. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

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

Why this priority

High severity
Remotely exploitable, no login, no user action
On your watchlist

A fixed release or distro patch exists.

Risk facts

CVSS score	7.5 (High)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	None
User interaction	None
EPSS exploit chance	2.4% (top 16%)
CISA exploited list	No
Weakness	CWE-835
Published	2026-05-12
Last modified	2026-10-26

Publisher (CNA): Microsoft Corporation · Vendor: microsoft

Last updated 2026-10-26 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2026-05-12 18:17 UTCPublished CVE record published
2026-10-26 18:10 UTCUpdated Record last modified

microsoft .net UPGRADE

Affected: >= 8.0.0 and < 8.0.27 · >= 9.0.0 and < 9.0.16 · >= 10.0.0 and < 10.0.8

Fixed in: 8.0.27, 9.0.16, 10.0.8

Safe to downgrade to: a release before 8.0.0

1. Check installed version

apt-cache policy .net || rpm -q .net || .net --version

2. UPGRADE to 8.0.27 (Debian / Ubuntu)

sudo apt update && sudo apt install --only-upgrade .net

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade .net

Note

Distros often backport fixes without changing the version number. Confirm with the distro advisory or changelog.

3. If no update is available yet, DOWNGRADE to a release before 8.0.0 (Debian / Ubuntu)

apt-cache madison .net sudo apt install .net=<VERSION_BEFORE_8.0.0> sudo apt-mark hold .net

3. If no update is available yet, DOWNGRADE (RHEL / Amazon Linux / Fedora)

dnf --showduplicates list .net sudo dnf downgrade .net-<VERSION_BEFORE_8.0.0> sudo dnf versionlock add .net

Downgrade risk

Downgrading can break dependent software and may reopen older bugs. Read the distro advisory first and test on a non-production host.

After downgrade

Restart the service, and keep the package held until a fixed release ships.

Exact fixes by distribution

NuGet (.NET) · Microsoft.AspNetCore.App.Runtime.win-arm · FIXED · 8.0.27 · vulnerable: >= 8.0.0, <= 8.0.26 · source

dotnet add package Microsoft.AspNetCore.App.Runtime.win-arm --version 8.0.27

NuGet (.NET) · Microsoft.AspNetCore.App.Runtime.win-arm64 · FIXED · 8.0.27 · vulnerable: >= 8.0.0, <= 8.0.26 · source

dotnet add package Microsoft.AspNetCore.App.Runtime.win-arm64 --version 8.0.27

NuGet (.NET) · Microsoft.AspNetCore.App.Runtime.win-x64 · FIXED · 8.0.27 · vulnerable: >= 8.0.0, <= 8.0.26 · source

dotnet add package Microsoft.AspNetCore.App.Runtime.win-x64 --version 8.0.27

NuGet (.NET) · Microsoft.AspNetCore.App.Runtime.win-x86 · FIXED · 8.0.27 · vulnerable: >= 8.0.0, <= 8.0.26 · source

dotnet add package Microsoft.AspNetCore.App.Runtime.win-x86 --version 8.0.27

NuGet (.NET) · Microsoft.AspNetCore.App.Runtime.linux-arm · FIXED · 8.0.27 · vulnerable: >= 8.0.0, <= 8.0.26 · source

dotnet add package Microsoft.AspNetCore.App.Runtime.linux-arm --version 8.0.27

NuGet (.NET) · Microsoft.AspNetCore.App.Runtime.linux-arm64 · FIXED · 8.0.27 · vulnerable: >= 8.0.0, <= 8.0.26 · source

dotnet add package Microsoft.AspNetCore.App.Runtime.linux-arm64 --version 8.0.27

Fedora ELN · xfsdump · FIXED · 3.3.0-3.eln159 · FEDORA-2026-6e9bb3f901 · source

sudo dnf upgrade --advisory=FEDORA-2026-6e9bb3f901

Fedora 46 · fio · FIXED · 3.43-2.fc46 · FEDORA-2026-b36219886b · source

sudo dnf upgrade --advisory=FEDORA-2026-b36219886b

RHEL 10 · dotnet8.0 · FIXED · dotnet8.0-8.0.127-1.el10_2

sudo dnf upgrade --advisory=RHSA-2026:21286 rpm -q dotnet8.0

RHEL 10 · dotnet9.0 · FIXED · dotnet9.0-9.0.117-1.el10_2

sudo dnf upgrade --advisory=RHSA-2026:21754 rpm -q dotnet9.0

RHEL 10 · dotnet10.0 · FIXED · dotnet10.0-10.0.108-1.el10_2

sudo dnf upgrade --advisory=RHSA-2026:22145 rpm -q dotnet10.0

RHEL 10.0 Extended Update Support · dotnet8.0 · FIXED · dotnet8.0-8.0.127-1.el10_0

sudo dnf upgrade --advisory=RHSA-2026:24332 rpm -q dotnet8.0

RHEL 10.0 Extended Update Support · dotnet9.0 · FIXED · dotnet9.0-9.0.117-1.el10_0

sudo dnf upgrade --advisory=RHSA-2026:24333 rpm -q dotnet9.0

Alpine 3.21 · dotnet8-runtime · FIXED · dotnet8-runtime-8.0.27-r0

apk add --upgrade dotnet8-runtime apk info -v dotnet8-runtime

Alpine 3.21 · dotnet9-runtime · FIXED · dotnet9-runtime-9.0.16-r0

apk add --upgrade dotnet9-runtime apk info -v dotnet9-runtime

Alpine 3.22 · dotnet8-runtime · FIXED · dotnet8-runtime-8.0.27-r0

apk add --upgrade dotnet8-runtime apk info -v dotnet8-runtime

Alpine 3.22 · dotnet9-runtime · FIXED · dotnet9-runtime-9.0.16-r0

apk add --upgrade dotnet9-runtime apk info -v dotnet9-runtime

Amazon Linux 2023 · see advisory · FIXED · ALAS2023-2026-1804 · source

sudo dnf update --advisory=ALAS2023-2026-1804

.NET 8.0 installed on Windows · KB5093447 · FIXED · 8.0.27 · KB5093447 · source

Install KB5093447 via Windows Update, then verify: Get-HotFix -Id KB5093447

.NET 8.0 installed on Mac OS · KB5093447 · FIXED · 8.0.27 · KB5093447 · source

Install KB5093447 via Windows Update, then verify: Get-HotFix -Id KB5093447

.NET 8.0 installed on Linux · KB5093447 · FIXED · 8.0.27 · KB5093447 · source

Install KB5093447 via Windows Update, then verify: Get-HotFix -Id KB5093447

.NET 9.0 installed on Linux · KB5093448 · FIXED · 9.0.16 · KB5093448 · source

Install KB5093448 via Windows Update, then verify: Get-HotFix -Id KB5093448

.NET 9.0 installed on Windows · KB5093448 · FIXED · 9.0.16 · KB5093448 · source

Install KB5093448 via Windows Update, then verify: Get-HotFix -Id KB5093448

Advisories and coverage

Official advisories

AlmaLinux Errata: [ALSA-2026:21297] Important: .NET 10.0 security update 2026-05-29
AlmaLinux Errata: [ALSA-2026:21296] Important: .NET 9.0 security update 2026-05-29
AlmaLinux Errata: [ALSA-2026:21293] Important: .NET 8.0 security update 2026-05-28

Verify at the official source NVD · CVE Program · Report a problem with this page
Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.

Quick answers

How do I fix CVE-2026-42899?

.net: upgrade to 8.0.27, 9.0.16, 10.0.8. Exact commands for each OS are on this page.

Is CVE-2026-42899 being exploited?

CVE-2026-42899 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

What does CVE-2026-42899 affect?

CVE-2026-42899 affects .net. Severity is high (CVSS 7.5). Loop with unreachable exit condition ('infinite loop') in ASP.NET Core allows an unauthorized attacker to deny service over a network.

How urgent is CVE-2026-42899?

Priority 57/100. High severity; Remotely exploitable, no login, no user action; On your watchlist

Software pages

.NET vulnerabilities

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References

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