title: Microsoft ASP.NET Core Security Feature Bypass Vulnerability
description: <p>A security feature bypass vulnerability exists in the way Microsoft ASP.NET Core parses encoded cookie names.</p>
<p>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.</p>
<p>The security update addresses the vulnerability by fixing the way the ASP.NET Core cookie parser handles encoded names.</p>
problem types: Security Feature Bypass
affected:
{
vendor: Microsoft
product: ASP.NET Core 2.1
cpes: cpe:2.3:a:microsoft:asp.net_core:2.1*:*:*:*:*:*:*:*
platforms: Unknown
versions:
version: 2.0, lessThan: publication, versionType: custom, status: affected
}
{
vendor: Microsoft
product: ASP.NET Core 3.1
cpes: cpe:2.3:a:microsoft:asp.net_core:3.1:*:*:*:*:*:*:*
platforms: Unknown
versions:
version: 3.0, lessThan: publication, versionType: custom, status: affected
}
metrics:
format: CVSS
scenarios: GENERAL
cvssV3_1: [
version: 3.1
baseSeverity: HIGH
baseScore: 7.5
vectorString: 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
]