CVE-2020-1045

Cookie parsing failure

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., aka 'Microsoft ASP.NET Core Security Feature Bypass Vulnerability'.

CVE-2020-1045 has a CVSS score of 7.5 (High). The vector is network-reachable, no privileges required, and no user interaction. A CVSS score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether this affects your application depends on whether the vulnerable code is present and reachable in your environment. A fixed version is available (2.1.22, 4.1.1, 3.1.8); upgrading removes the vulnerable code path.

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1. What is CVE-2020-1045? CVE-2020-1045 is a high-severity security vulnerability in Microsoft.AspNetCore.App (nuget), affecting versions <= 2.1.21. It is fixed in 2.1.22, 4.1.1, 3.1.8.
2. How severe is CVE-2020-1045? CVE-2020-1045 has a CVSS score of 7.5 (High). This score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether it represents real risk in your environment depends on whether the vulnerable code is present and reachable.
3. Which packages are affected by CVE-2020-1045?
   • Microsoft.AspNetCore.App (nuget) (versions <= 2.1.21)
   • Microsoft.Owin (nuget) (versions < 4.1.1)
   • Microsoft.AspNetCore.App.Runtime.linux-arm (nuget) (versions >= 3.1.0, < 3.1.8)
   • Microsoft.AspNetCore.App.Runtime.linux-arm64 (nuget) (versions >= 3.1.0, < 3.1.8)
   • Microsoft.AspNetCore.App.Runtime.linux-musl-arm64 (nuget) (versions >= 3.1.0, < 3.1.8)
   • Microsoft.AspNetCore.App.Runtime.linux-musl-x64 (nuget) (versions >= 3.1.0, < 3.1.8)
   • Microsoft.AspNetCore.App.Runtime.linux-x64 (nuget) (versions >= 3.1.0, < 3.1.8)
   • Microsoft.AspNetCore.App.Runtime.osx-x64 (nuget) (versions >= 3.1.0, < 3.1.8)
   • Microsoft.AspNetCore.App.Runtime.win-arm (nuget) (versions >= 3.1.0, < 3.1.8)
   • Microsoft.AspNetCore.App.Runtime.win-x64 (nuget) (versions >= 3.1.0, < 3.1.8)
   • Microsoft.AspNetCore.App.Runtime.win-x86 (nuget) (versions >= 3.1.0, < 3.1.8)
   • Microsoft.AspNetCore.App.Runtime.win-arm64 (nuget) (versions >= 3.1.5, < 3.1.8)
   • Microsoft.AspNetCore.Http (nuget) (versions < 2.1.22)
4. Is there a fix for CVE-2020-1045? Yes. CVE-2020-1045 is fixed in 2.1.22, 4.1.1, 3.1.8. Upgrade to this version or later.
5. Is CVE-2020-1045 exploitable, and should I be worried? Whether CVE-2020-1045 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
6. What actually determines whether CVE-2020-1045 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
7. How do I fix CVE-2020-1045?
   • Upgrade Microsoft.AspNetCore.App to 2.1.22 or later
   • Upgrade Microsoft.Owin to 4.1.1 or later
   • Upgrade Microsoft.AspNetCore.App.Runtime.linux-arm to 3.1.8 or later
   • Upgrade Microsoft.AspNetCore.App.Runtime.linux-arm64 to 3.1.8 or later
   • Upgrade Microsoft.AspNetCore.App.Runtime.linux-musl-arm64 to 3.1.8 or later
   • Upgrade Microsoft.AspNetCore.App.Runtime.linux-musl-x64 to 3.1.8 or later
   • Upgrade Microsoft.AspNetCore.App.Runtime.linux-x64 to 3.1.8 or later
   • Upgrade Microsoft.AspNetCore.App.Runtime.osx-x64 to 3.1.8 or later
   • Upgrade Microsoft.AspNetCore.App.Runtime.win-arm to 3.1.8 or later
   • Upgrade Microsoft.AspNetCore.App.Runtime.win-x64 to 3.1.8 or later
   • Upgrade Microsoft.AspNetCore.App.Runtime.win-x86 to 3.1.8 or later
   • Upgrade Microsoft.AspNetCore.App.Runtime.win-arm64 to 3.1.8 or later
   • Upgrade Microsoft.AspNetCore.Http to 2.1.22 or later

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