CVE-2019-0820: System.Text.RegularExpressions Denial of Service Vulnerability

HIGH
Advisory Identifier: GHSA-cmhx-cq75-c4mj
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CVSS 7.5
CWE-400 CWE-1333
Published
Advisory Summary

CVE-2019-0820 is a HIGH (CVSS 7.5) denial of service vulnerability (CWE-400: Uncontrolled Resource Consumption) affecting System.Text.RegularExpressions libraries in the NuGet ecosystem. The issue involves regular expression denial of service in system.text.regularexpressions. Remediation is available by upgrading affected packages to version 4.3.1.

CVE-2019-0820 at a Glance

CVE Identifier CVE-2019-0820
GHSA Identifier GHSA-cmhx-cq75-c4mj
Severity HIGH
CVSS v3.1 Base Score 7.5
CWE Classification CWE-400: Uncontrolled Resource Consumption
Affected Product System.Text.RegularExpressions
Package Ecosystem NuGet
Published Date
Last Updated

Security Impact

CVSS: 7.5

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:N/I:N/A:H).

Attack Vector Network (AV:N)
Attack Complexity Low (AC:L)
Privileges Required None (PR:N)
User Interaction None (UI:N)
Scope Unchanged (S:U)
Confidentiality None (C:N)
Integrity None (I:N)
Availability High (A:H)

How to Fix CVE-2019-0820

To remediate this vulnerability, upgrade all affected System.Text.RegularExpressions dependencies to a patched release. Both direct and transitive dependencies should be checked, as frameworks or security libraries may pull in vulnerable versions transitively.

System.Text.RegularExpressions fixed: 4.3.1 
Upgrade System.Text.RegularExpressions to 4.3.1
Verify Direct and Transitive Dependencies

Run the following command in your project directory to verify that all resolved dependencies use the patched release: 

inspect dependencies for System.Text.RegularExpressions

How to Check if You Are Affected

To determine whether your application is affected by CVE-2019-0820, inspect your project dependencies for System.Text.RegularExpressions:

inspect dependencies for System.Text.RegularExpressions

Analyze the terminal output to locate any version of System.Text.RegularExpressions in your dependency tree. If any resolved version matches the vulnerable ranges listed in the table below (for example, versions earlier than 4.3.1), 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 CWE-400: Uncontrolled Resource Consumption, where the product does not properly control the allocation and maintenance of a limited resource. In System.Text.RegularExpressions, 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

A denial of service vulnerability exists when .NET Framework and .NET Core improperly process RegEx strings, aka '.NET Framework and .NET Core Denial of Service Vulnerability'. This CVE ID is unique from CVE-2019-0980, CVE-2019-0981.

CVE-2019-0820 Affected System.Text.RegularExpressions Versions

1 component(s)
Fixed Versions:
4.3.1
Product / Package Ecosystem Affected Versions Fixed Version
System.Text.RegularExpressions
nuget/System.Text.RegularExpressions
NuGet
≥ 4.3.0
< 4.3.1
4.3.1

References

NVD — CVE-2019-0820 NVD
https://nvd.nist.gov/vuln/detail/CVE-2019-0820
access.redhat.com/errata/rhsa-2019:12... WEB
https://access.redhat.com/errata/RHSA-2019:1259
System.Text.RegularExpressions Security Information SECURITY
https://portal.msrc.microsoft.com/en-US/security-guidance/advisory/CVE-2019-0820

Frequently Asked Questions

What is CVE-2019-0820?
CVE-2019-0820 is a security vulnerability in System.Text.RegularExpressions involving Regular Expression Denial of Service in System.Text.RegularExpressions under CWE-400: Uncontrolled Resource Consumption.
Which System.Text.RegularExpressions versions are affected?
Affected versions include releases prior to 4.3.1 across affected packages: System.Text.RegularExpressions.
What version fixes CVE-2019-0820?
Upgrading to 4.3.1 (or the latest patched release for your respective branch) resolves the vulnerability.
Is System.Text.RegularExpressions affected?
Yes, System.Text.RegularExpressions is affected in releases prior to 4.3.1. Upgrade your dependency to 4.3.1 or later.
What is the CVSS score of CVE-2019-0820?
CVE-2019-0820 has a CVSS v3.1 base score of 7.5 (HIGH) with vector string CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H.
What CWE is associated with CVE-2019-0820?
CVE-2019-0820 is classified under CWE-400: Uncontrolled Resource Consumption (The product does not properly control the allocation and maintenance of a limited resource.).
How can I check NuGet dependencies for CVE-2019-0820?
Run the dependency tree command: 'inspect dependencies for System.Text.RegularExpressions'. This command lists direct and transitive dependencies in your build configuration so you can verify if a vulnerable version is resolved.
Machine-readable OSV JSON OSV v1.5 Schema
Normalized schema output
View Raw JSON 
{
  "schema_version" : "1.4.0",
  "id" : "GHSA-cmhx-cq75-c4mj",
  "modified" : "2023-02-21T18:57:08Z",
  "published" : "2021-08-04T21:03:46Z",
  "aliases" : [ "CVE-2019-0820" ],
  "summary" : "Regular Expression Denial of Service in System.Text.RegularExpressions",
  "details" : "A denial of service vulnerability exists when .NET Framework and .NET Core improperly process RegEx strings, aka '.NET Framework and .NET Core Denial of Service Vulnerability'. This CVE ID is unique from CVE-2019-0980, CVE-2019-0981.",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "NuGet",
      "name" : "System.Text.RegularExpressions"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "4.3.0"
      }, {
        "fixed" : "4.3.1"
      } ]
    } ]
  } ],
  "references" : [ {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2019-0820"
  }, {
    "type" : "WEB",
    "url" : "https://access.redhat.com/errata/RHSA-2019:1259"
  }, {
    "type" : "WEB",
    "url" : "https://portal.msrc.microsoft.com/en-US/security-guidance/advisory/CVE-2019-0820"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-1333", "CWE-400" ],
    "severity" : "HIGH",
    "github_reviewed" : true,
    "github_reviewed_at" : "2021-08-04T21:03:27Z",
    "nvd_published_at" : "2019-05-16T19:29:00Z"
  }
}