# CVE-2021-26701: .NET Core Remote Code Execution Vulnerability > Attackers can execute arbitrary code via a vulnerability in the .NET Core runtime, affecting developers and users of .NET applications. - **Severity:** High 8.1 (`CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H/E:U/RL:O/RC:C`) - **Exploited in the wild:** Not known - **Login needed:** Not needed - **Attackable:** Over the internet - **Victim action needed:** Not needed - **Fix available:** Yes - **Published:** 25 Feb 2021 - **Updated:** 28 May 2026 - **Also known as:** BIT-dotnet-2021-26701, BIT-dotnet-sdk-2021-26701, ECHO-1fd9-6799-b020, GHSA-ghhp-997w-qr28, RHSA-2021:0787, RHSA-2021:0788, RHSA-2021:0789, RHSA-2021:0790, RHSA-2021:0793, RHSA-2021:0794 ## What is CVE-2021-26701? CVE-2021-26701 is a high-severity code injection vulnerability in Fedoraproject Fedora, published on 25 Feb 2021. An attacker can exploit it over the internet without logging in, with no action from the victim. ### Official description .NET Core Remote Code Execution Vulnerability ## Which versions are affected by CVE-2021-26701? 8 open source packages ship an affected version, including System.Text.Encodings.Web, dotnet and dotnet-sdk. It affects 5 products. | Package | Ecosystem | Affected | Fixed in | | --- | --- | --- | --- | | `System.Text.Encodings.Web` | NuGet | From 4.0.0 | 4.5.1 | | `System.Text.Encodings.Web` | NuGet | From 4.0.0 | 4.5.1 | | `System.Text.Encodings.Web` | NuGet | From 4.6.0 | 4.7.2 | | `System.Text.Encodings.Web` | NuGet | From 4.6.0 | 4.7.2 | | `System.Text.Encodings.Web` | NuGet | From 5.0.0 | 5.0.1 | | `System.Text.Encodings.Web` | NuGet | From 5.0.0 | 5.0.1 | | `dotnet` | Bitnami | From 5.0.0 | 5.0.4 | | `dotnet-sdk` | Bitnami | From 5.0.0 | 5.0.4 | | `aspnetcore-runtime-3.1` | Red Hat:enterprise_linux:8::appstream | All versions | 0:3.1.13-1.el8_3 | | `aspnetcore-runtime-5.0` | Red Hat:enterprise_linux:8::appstream | All versions | 0:5.0.4-1.el8_3 | | `aspnetcore-targeting-pack-3.1` | Red Hat:enterprise_linux:8::appstream | All versions | 0:3.1.13-1.el8_3 | | `aspnetcore-targeting-pack-5.0` | Red Hat:enterprise_linux:8::appstream | All versions | 0:5.0.4-1.el8_3 | | `dotnet` | Red Hat:enterprise_linux:8::appstream | All versions | 0:2.1.522-1.el8_3 | | `dotnet` | Red Hat:enterprise_linux:8::appstream | All versions | 0:5.0.104-1.el8_3 | | `dotnet-apphost-pack-3.1` | Red Hat:enterprise_linux:8::appstream | All versions | 0:3.1.13-1.el8_3 | | `dotnet-apphost-pack-3.1-debuginfo` | Red Hat:enterprise_linux:8::appstream | All versions | 0:3.1.13-1.el8_3 | | `dotnet-apphost-pack-5.0` | Red Hat:enterprise_linux:8::appstream | All versions | 0:5.0.4-1.el8_3 | | `dotnet-apphost-pack-5.0-debuginfo` | Red Hat:enterprise_linux:8::appstream | All versions | 0:5.0.4-1.el8_3 | | `dotnet-debuginfo` | Red Hat:enterprise_linux:8::appstream | All versions | 0:2.1.522-1.el8_3 | | `dotnet-debugsource` | Red Hat:enterprise_linux:8::appstream | All versions | 0:2.1.522-1.el8_3 | | `dotnet-host` | Red Hat:enterprise_linux:8::appstream | All versions | 0:5.0.4-1.el8_3 | | `dotnet-host-debuginfo` | Red Hat:enterprise_linux:8::appstream | All versions | 0:5.0.4-1.el8_3 | | `dotnet-host-fxr-2.1` | Red Hat:enterprise_linux:8::appstream | All versions | 0:2.1.26-1.el8_3 | | `dotnet-host-fxr-2.1-debuginfo` | Red Hat:enterprise_linux:8::appstream | All versions | 0:2.1.26-1.el8_3 | | `dotnet-hostfxr-3.1` | Red Hat:enterprise_linux:8::appstream | All versions | 0:3.1.13-1.el8_3 | | `dotnet-hostfxr-3.1-debuginfo` | Red Hat:enterprise_linux:8::appstream | All versions | 0:3.1.13-1.el8_3 | | `dotnet-hostfxr-5.0` | Red Hat:enterprise_linux:8::appstream | All versions | 0:5.0.4-1.el8_3 | | `dotnet-hostfxr-5.0-debuginfo` | Red Hat:enterprise_linux:8::appstream | All versions | 0:5.0.4-1.el8_3 | | `dotnet-runtime-2.1` | Red Hat:enterprise_linux:8::appstream | All versions | 0:2.1.26-1.el8_3 | | `dotnet-runtime-2.1-debuginfo` | Red Hat:enterprise_linux:8::appstream | All versions | 0:2.1.26-1.el8_3 | | `dotnet-runtime-3.1` | Red Hat:enterprise_linux:8::appstream | All versions | 0:3.1.13-1.el8_3 | | `dotnet-runtime-3.1-debuginfo` | Red Hat:enterprise_linux:8::appstream | All versions | 0:3.1.13-1.el8_3 | | `dotnet-runtime-5.0` | Red Hat:enterprise_linux:8::appstream | All versions | 0:5.0.4-1.el8_3 | | `dotnet-runtime-5.0-debuginfo` | Red Hat:enterprise_linux:8::appstream | All versions | 0:5.0.4-1.el8_3 | | `dotnet-sdk-2.1` | Red Hat:enterprise_linux:8::appstream | All versions | 0:2.1.522-1.el8_3 | | `dotnet-sdk-2.1.5xx` | Red Hat:enterprise_linux:8::appstream | All versions | 0:2.1.522-1.el8_3 | | `dotnet-sdk-2.1.5xx-debuginfo` | Red Hat:enterprise_linux:8::appstream | All versions | 0:2.1.522-1.el8_3 | | `dotnet-sdk-3.1` | Red Hat:enterprise_linux:8::appstream | All versions | 0:3.1.113-1.el8_3 | | `dotnet-sdk-3.1-debuginfo` | Red Hat:enterprise_linux:8::appstream | All versions | 0:3.1.113-1.el8_3 | | `dotnet-sdk-5.0` | Red Hat:enterprise_linux:8::appstream | All versions | 0:5.0.104-1.el8_3 | Products: Fedoraproject Fedora, Microsoft .Net, Microsoft .Net Core, Microsoft Powershell Core, Microsoft Visual Studio 2019. ## How do I fix CVE-2021-26701? Upgrade System.Text.Encodings.Web to a fixed version for your release line: 4.5.1, 4.7.2 or 5.0.1. ## Is CVE-2021-26701 being exploited? There is no known exploitation of CVE-2021-26701 in the wild and no public exploit code. ## Other vulnerabilities in Fedoraproject Fedora - [CVE-2024-4577](https://insights.sbomify.com/CVE-2024-4577/): PHP-CGI OS Command Injection (critical 9.8, exploited in the wild) - [CVE-2021-39226](https://insights.sbomify.com/CVE-2021-39226/): Grafana Authentication Bypass (critical 9.8, exploited in the wild) - [CVE-2019-5544](https://insights.sbomify.com/CVE-2019-5544/): VMware ESXi and Horizon DaaS OpenSLP Heap-Based Buffer Overflow (critical 9.8, exploited in the wild) - [CVE-2024-4947](https://insights.sbomify.com/CVE-2024-4947/): Google Chromium V8 Type Confusion (critical 9.6, exploited in the wild) - [CVE-2024-4671](https://insights.sbomify.com/CVE-2024-4671/): Google Chromium Visuals Use-After-Free (critical 9.6, exploited in the wild) ## Fix prompt for AI coding agents ```text Check this codebase for CVE-2021-26701 and fix it if it is affected. What it is: CVE-2021-26701 is a high-severity code injection vulnerability in Fedoraproject Fedora, published on 25 Feb 2021. 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-2021-26701 in the wild and no public exploit code. Affected packages and fixed versions: - System.Text.Encodings.Web (NuGet): affected from 4.0.0; fixed in 4.5.1 - System.Text.Encodings.Web (NuGet): affected from 4.0.0; fixed in 4.5.1 - System.Text.Encodings.Web (NuGet): affected from 4.6.0; fixed in 4.7.2 - System.Text.Encodings.Web (NuGet): affected from 4.6.0; fixed in 4.7.2 - System.Text.Encodings.Web (NuGet): affected from 5.0.0; fixed in 5.0.1 - System.Text.Encodings.Web (NuGet): affected from 5.0.0; fixed in 5.0.1 - dotnet (Bitnami): affected from 5.0.0; fixed in 5.0.4 - dotnet-sdk (Bitnami): affected from 5.0.0; fixed in 5.0.4 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-2021-26701/ (Markdown: https://insights.sbomify.com/CVE-2021-26701/index.md) ``` ## Sources - CVE record: https://www.cve.org/CVERecord?id=CVE-2021-26701 - NVD: https://nvd.nist.gov/vuln/detail/CVE-2021-26701 - OSV: https://osv.dev/vulnerability/CVE-2021-26701 --- From sbomify Insights: https://insights.sbomify.com/CVE-2021-26701/ Summaries are generated and may contain mistakes; the official description above is the record.