CVE-2021-26701: System.Text.Encodings.Web Remote Code Execution Vulnerability
CRITICALCVE-2021-26701 is a CRITICAL (CVSS 9.8) remote code execution vulnerability (General Security Weakness) affecting System.Text.Encodings.Web libraries in the NuGet ecosystem. The issue involves .net core remote code execution vulnerability. Remediation is available by upgrading affected packages to version 4.5.1, 4.7.2, 5.0.1.
CVE-2021-26701 at a Glance
Security Impact
CVSS: 9.8
The security impact metrics below are parsed directly from the CVSS v3.1 vector string (CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H).
How to Fix CVE-2021-26701
To remediate this vulnerability, upgrade all affected System.Text.Encodings.Web dependencies to a patched release. Both direct and transitive dependencies should be checked, as frameworks or security libraries may pull in vulnerable versions transitively.
Upgrade System.Text.Encodings.Web to 4.5.1
Upgrade System.Text.Encodings.Web to 4.7.2
Upgrade System.Text.Encodings.Web to 5.0.1
Run the following command in your project directory to verify that all resolved dependencies use the patched release:
inspect dependencies for System.Text.Encodings.Web
How to Check if You Are Affected
To determine whether your application is affected by CVE-2021-26701, inspect your project dependencies for System.Text.Encodings.Web:
inspect dependencies for System.Text.Encodings.Web
Analyze the terminal output to locate any version of System.Text.Encodings.Web in your dependency tree. If any resolved version matches the vulnerable ranges listed in the table below (for example, versions earlier than 4.5.1), your application is affected.
Note: Verify declared build manifests and deployed runtime container environments.
Technical Details
Vulnerability Mechanism & Technical Analysis
This vulnerability is classified under General Security Weakness. In System.Text.Encodings.Web, software state validation or input boundaries are circumvented during processing. Review the official source advisory statement below for specific affected components, classes, and reproduction details.
Source Advisory Statement
CVE-2021-26701 Affected System.Text.Encodings.Web Versions
3 component(s)| Product / Package | Ecosystem | Affected Versions | Fixed Version |
|---|---|---|---|
|
System.Text.Encodings.Web
|
NuGet |
≥ 4.0.0
< 4.5.1
|
4.5.1
|
|
System.Text.Encodings.Web
|
NuGet |
≥ 4.6.0
< 4.7.2
|
4.7.2
|
|
System.Text.Encodings.Web
|
NuGet |
≥ 5.0.0
< 5.0.1
All 1 versions
5.0.0
|
5.0.1
|
References
Frequently Asked Questions
What is CVE-2021-26701?
Which System.Text.Encodings.Web versions are affected?
What version fixes CVE-2021-26701?
Is System.Text.Encodings.Web affected?
What is the CVSS score of CVE-2021-26701?
What CWE is associated with CVE-2021-26701?
How can I check NuGet dependencies for CVE-2021-26701?
Machine-readable OSV JSON
OSV v1.5 Schema
{
"schema_version" : "1.4.0",
"id" : "GHSA-ghhp-997w-qr28",
"modified" : "2021-04-21T19:37:39Z",
"published" : "2021-04-21T19:38:01Z",
"aliases" : [ "CVE-2021-26701" ],
"summary" : ".NET Core Remote Code Execution Vulnerability",
"details" : ".NET Core Remote Code Execution Vulnerability This CVE ID is unique from CVE-2021-24112.\n\n### Executive summary\n\nMicrosoft 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.\n\nA remote code execution vulnerability exists in .NET 5 and .NET Core due to how text encoding is performed.\n\n### Discussion\n\nDiscussion for this issue can be found at dotnet/runtime#49377\n\n### Mitigation factors\n\nMicrosoft has not identified any mitigating factors for this vulnerability.\n\n### Affected software\n\nThe vulnerable package is `System.Text.Encodings.Web` . Upgrading your package and redeploying your app should be sufficient to address this vulnerability.\n\nVulnerable package versions:\n\nAny .NET 5, .NET Core, or .NET Framework based application that uses the System.Text.Encodings.Web package with a vulnerable version listed below.\n\nPackage Name | Vulnerable Versions | Secure Versions\n-|-|-\nSystem.Text.Encodings.Web | 4.0.0 - 4.5.0 | 4.5.1\nSystem.Text.Encodings.Web | 4.6.0-4.7.1 | 4.7.2\nSystem.Text.Encodings.Web | 5.0.0 | 5.0.1\n\n\nPlease validate that each of the .NET versions you are using is in support. Security updates are only provided for supported .NET versions.\n\n",
"severity" : [ {
"type" : "CVSS_V3",
"score" : "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H"
} ],
"affected" : [ {
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},
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"versions" : [ "5.0.0" ]
} ],
"references" : [ {
"type" : "ADVISORY",
"url" : "https://nvd.nist.gov/vuln/detail/CVE-2021-26701"
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"url" : "https://github.com/dotnet/announcements/issues/178"
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}, {
"type" : "WEB",
"url" : "https://portal.msrc.microsoft.com/en-US/security-guidance/advisory/CVE-2021-26701"
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"database_specific" : {
"cwe_ids" : [ ],
"severity" : "CRITICAL",
"github_reviewed" : true,
"github_reviewed_at" : "2021-04-21T19:37:39Z",
"nvd_published_at" : "2021-02-25T23:15:00Z"
}
}