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.NET Core Remote Code Execution Vulnerability

Critical severity GitHub Reviewed Published Apr 21, 2021 to the GitHub Advisory Database • Updated Jan 7, 2024

Package

nuget System.Text.Encodings.Web (NuGet)

Affected versions

>= 4.0.0, < 4.5.1
>= 4.6.0, < 4.7.2
= 5.0.0

Patched versions

4.5.1
4.7.2
5.0.1

Description

.NET Core Remote Code Execution Vulnerability This CVE ID is unique from CVE-2021-24112.

Executive summary

Microsoft is releasing this security advisory to provide information about a vulnerability in .NET 5.0, .NET Core 3.1, and .NET Core 2.1. This advisory also provides guidance on what developers can do to update their applications to remove this vulnerability.

A remote code execution vulnerability exists in .NET 5 and .NET Core due to how text encoding is performed.

Discussion

Discussion for this issue can be found at dotnet/runtime#49377

Mitigation factors

Microsoft has not identified any mitigating factors for this vulnerability.

Affected software

The vulnerable package is System.Text.Encodings.Web . Upgrading your package and redeploying your app should be sufficient to address this vulnerability.

Vulnerable package versions:

Any .NET 5, .NET Core, or .NET Framework based application that uses the System.Text.Encodings.Web package with a vulnerable version listed below.

Package Name Vulnerable Versions Secure Versions
System.Text.Encodings.Web 4.0.0 - 4.5.0 4.5.1
System.Text.Encodings.Web 4.6.0-4.7.1 4.7.2
System.Text.Encodings.Web 5.0.0 5.0.1

Please validate that each of the .NET versions you are using is in support. Security updates are only provided for supported .NET versions.

References

Published by the National Vulnerability Database Feb 25, 2021
Reviewed Apr 21, 2021
Published to the GitHub Advisory Database Apr 21, 2021
Last updated Jan 7, 2024

Severity

Critical

CVSS overall score

This score calculates overall vulnerability severity from 0 to 10 and is based on the Common Vulnerability Scoring System (CVSS).
/ 10

CVSS v3 base metrics

Attack vector
Network
Attack complexity
Low
Privileges required
None
User interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
High

CVSS v3 base metrics

Attack vector: More severe the more the remote (logically and physically) an attacker can be in order to exploit the vulnerability.
Attack complexity: More severe for the least complex attacks.
Privileges required: More severe if no privileges are required.
User interaction: More severe when no user interaction is required.
Scope: More severe when a scope change occurs, e.g. one vulnerable component impacts resources in components beyond its security scope.
Confidentiality: More severe when loss of data confidentiality is highest, measuring the level of data access available to an unauthorized user.
Integrity: More severe when loss of data integrity is the highest, measuring the consequence of data modification possible by an unauthorized user.
Availability: More severe when the loss of impacted component availability is highest.
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

EPSS score

8.067%
(94th percentile)

Weaknesses

No CWEs

CVE ID

CVE-2021-26701

GHSA ID

GHSA-ghhp-997w-qr28

Source code

No known source code
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