# CVE-2020-1045: Microsoft ASP.NET Core Security Feature Bypass Vulnerability > Attackers can bypass cookie security features by exploiting improper parsing of encoded cookie names in ASP.NET Core. - **Severity:** High 7.5 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N/E:P/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:** 11 Sep 2020 - **Updated:** 18 Nov 2024 - **Also known as:** BIT-aspnet-core-2020-1045, ECHO-cb59-aca0-0cd8, GHSA-hxrm-9w7p-39cc, RHSA-2020:3697, RHSA-2020:3699 ## What is CVE-2020-1045? CVE-2020-1045 is a high-severity vulnerability in Fedoraproject Fedora, published on 11 Sep 2020. An attacker can exploit it over the internet without logging in, with no action from the victim. ### Official description

A security feature bypass vulnerability exists in the way Microsoft ASP.NET Core parses encoded cookie names.

The ASP.NET Core cookie parser decodes entire cookie strings which could allow a malicious attacker to set a second cookie with the name being percent encoded.

The security update addresses the vulnerability by fixing the way the ASP.NET Core cookie parser handles encoded names.

## Which versions are affected by CVE-2020-1045? 27 open source packages ship an affected version, including Microsoft.AspNetCore.App, aspnet-core and Microsoft.AspNetCore.App.Runtime.linux-arm. It affects 6 products. | Package | Ecosystem | Affected | Fixed in | | --- | --- | --- | --- | | `Microsoft.AspNetCore.App` | NuGet | All versions | 2.1.22 | | `Microsoft.AspNetCore.App` | NuGet | All versions | 2.1.22 | | `aspnet-core` | Bitnami | From 3.1.0 | 3.1.8 | | `Microsoft.AspNetCore.App.Runtime.linux-arm` | NuGet | From 3.1.0 | 3.1.8 | | `Microsoft.AspNetCore.App.Runtime.linux-arm` | NuGet | From 3.1.0 | 3.1.8 | | `Microsoft.AspNetCore.App.Runtime.linux-arm64` | NuGet | From 3.1.0 | 3.1.8 | | `Microsoft.AspNetCore.App.Runtime.linux-arm64` | NuGet | From 3.1.0 | 3.1.8 | | `Microsoft.AspNetCore.App.Runtime.linux-musl-arm64` | NuGet | From 3.1.0 | 3.1.8 | | `Microsoft.AspNetCore.App.Runtime.linux-musl-arm64` | NuGet | From 3.1.0 | 3.1.8 | | `Microsoft.AspNetCore.App.Runtime.linux-musl-x64` | NuGet | From 3.1.0 | 3.1.8 | | `Microsoft.AspNetCore.App.Runtime.linux-musl-x64` | NuGet | From 3.1.0 | 3.1.8 | | `Microsoft.AspNetCore.App.Runtime.linux-x64` | NuGet | From 3.1.0 | 3.1.8 | | `Microsoft.AspNetCore.App.Runtime.linux-x64` | NuGet | From 3.1.0 | 3.1.8 | | `Microsoft.AspNetCore.App.Runtime.osx-x64` | NuGet | From 3.1.0 | 3.1.8 | | `Microsoft.AspNetCore.App.Runtime.osx-x64` | NuGet | From 3.1.0 | 3.1.8 | | `Microsoft.AspNetCore.App.Runtime.win-arm` | NuGet | From 3.1.0 | 3.1.8 | | `Microsoft.AspNetCore.App.Runtime.win-arm` | NuGet | From 3.1.0 | 3.1.8 | | `Microsoft.AspNetCore.App.Runtime.win-arm64` | NuGet | From 3.1.5 | 3.1.8 | | `Microsoft.AspNetCore.App.Runtime.win-arm64` | NuGet | From 3.1.5 | 3.1.8 | | `Microsoft.AspNetCore.App.Runtime.win-x64` | NuGet | From 3.1.0 | 3.1.8 | | `Microsoft.AspNetCore.App.Runtime.win-x64` | NuGet | From 3.1.0 | 3.1.8 | | `Microsoft.AspNetCore.App.Runtime.win-x86` | NuGet | From 3.1.0 | 3.1.8 | | `Microsoft.AspNetCore.App.Runtime.win-x86` | NuGet | From 3.1.0 | 3.1.8 | | `Microsoft.AspNetCore.Http` | NuGet | All versions | 2.1.22 | | `Microsoft.AspNetCore.Http` | NuGet | All versions | 2.1.22 | | `Microsoft.Owin` | NuGet | All versions | 4.1.1 | | `Microsoft.Owin` | NuGet | All versions | 4.1.1 | | `aspnetcore-runtime-3.1` | Red Hat:enterprise_linux:8::appstream | All versions | 0:3.1.8-2.el8_2 | | `aspnetcore-targeting-pack-3.1` | Red Hat:enterprise_linux:8::appstream | All versions | 0:3.1.8-2.el8_2 | | `dotnet` | Red Hat:enterprise_linux:8::appstream | All versions | 0:3.1.108-2.el8_2 | | `dotnet-apphost-pack-3.1` | Red Hat:enterprise_linux:8::appstream | All versions | 0:3.1.8-2.el8_2 | | `dotnet-apphost-pack-3.1-debuginfo` | Red Hat:enterprise_linux:8::appstream | All versions | 0:3.1.8-2.el8_2 | | `dotnet-host` | Red Hat:enterprise_linux:8::appstream | All versions | 0:3.1.8-2.el8_2 | | `dotnet-host-debuginfo` | Red Hat:enterprise_linux:8::appstream | All versions | 0:3.1.8-2.el8_2 | | `dotnet-hostfxr-3.1` | Red Hat:enterprise_linux:8::appstream | All versions | 0:3.1.8-2.el8_2 | | `dotnet-hostfxr-3.1-debuginfo` | Red Hat:enterprise_linux:8::appstream | All versions | 0:3.1.8-2.el8_2 | | `dotnet-runtime-3.1` | Red Hat:enterprise_linux:8::appstream | All versions | 0:3.1.8-2.el8_2 | | `dotnet-runtime-3.1-debuginfo` | Red Hat:enterprise_linux:8::appstream | All versions | 0:3.1.8-2.el8_2 | | `dotnet-sdk-3.1` | Red Hat:enterprise_linux:8::appstream | All versions | 0:3.1.108-2.el8_2 | | `dotnet-sdk-3.1-debuginfo` | Red Hat:enterprise_linux:8::appstream | All versions | 0:3.1.108-2.el8_2 | Products: Fedoraproject Fedora, Microsoft Asp.net Core, Redhat Enterprise Linux, Redhat Enterprise Linux Aus, Redhat Enterprise Linux Eus, Redhat Enterprise Linux Tus. ## How do I fix CVE-2020-1045? Upgrade Microsoft.AspNetCore.App to 2.1.22 or later. ## Is CVE-2020-1045 being exploited? There is no known exploitation of CVE-2020-1045 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-2020-1045 and fix it if it is affected. What it is: CVE-2020-1045 is a high-severity vulnerability in Fedoraproject Fedora, published on 11 Sep 2020. 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-2020-1045 in the wild and no public exploit code. Affected packages and fixed versions: - Microsoft.AspNetCore.App (NuGet): affected all versions; fixed in 2.1.22 - Microsoft.AspNetCore.App (NuGet): affected all versions; fixed in 2.1.22 - aspnet-core (Bitnami): affected from 3.1.0; fixed in 3.1.8 - Microsoft.AspNetCore.App.Runtime.linux-arm (NuGet): affected from 3.1.0; fixed in 3.1.8 - Microsoft.AspNetCore.App.Runtime.linux-arm (NuGet): affected from 3.1.0; fixed in 3.1.8 - Microsoft.AspNetCore.App.Runtime.linux-arm64 (NuGet): affected from 3.1.0; fixed in 3.1.8 - Microsoft.AspNetCore.App.Runtime.linux-arm64 (NuGet): affected from 3.1.0; fixed in 3.1.8 - Microsoft.AspNetCore.App.Runtime.linux-musl-arm64 (NuGet): affected from 3.1.0; fixed in 3.1.8 - Microsoft.AspNetCore.App.Runtime.linux-musl-arm64 (NuGet): affected from 3.1.0; fixed in 3.1.8 - Microsoft.AspNetCore.App.Runtime.linux-musl-x64 (NuGet): affected from 3.1.0; fixed in 3.1.8 - Microsoft.AspNetCore.App.Runtime.linux-musl-x64 (NuGet): affected from 3.1.0; fixed in 3.1.8 - Microsoft.AspNetCore.App.Runtime.linux-x64 (NuGet): affected from 3.1.0; fixed in 3.1.8 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-2020-1045/ (Markdown: https://insights.sbomify.com/CVE-2020-1045/index.md) ``` ## Sources - CVE record: https://www.cve.org/CVERecord?id=CVE-2020-1045 - NVD: https://nvd.nist.gov/vuln/detail/CVE-2020-1045 - OSV: https://osv.dev/vulnerability/CVE-2020-1045 --- From sbomify Insights: https://insights.sbomify.com/CVE-2020-1045/ Summaries are generated and may contain mistakes; the official description above is the record.