CVE-2020-28042: ServiceStack Signature Validation Bypass Vulnerability

MODERATE
Advisory Identifier: GHSA-v5rv-hpxg-8x49
Share
CWE-347
Published
Advisory Summary

CVE-2020-28042 is a MODERATE signature validation bypass vulnerability (CWE-347: Improper Verification of Cryptographic Signature) affecting ServiceStack libraries in the NuGet ecosystem. The issue involves signature validation bypass in servicestack. Remediation is available by upgrading affected packages to version 5.9.2.

CVE-2020-28042 at a Glance

CVE Identifier CVE-2020-28042
GHSA Identifier GHSA-v5rv-hpxg-8x49
Severity MODERATE
CVSS v3.1 Base Score N/A
CWE Classification CWE-347: Improper Verification of Cryptographic Signature
Affected Product ServiceStack
Package Ecosystem NuGet
Published Date
Last Updated

How to Fix CVE-2020-28042

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

ServiceStack fixed: 5.9.2 
Upgrade ServiceStack to 5.9.2
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 ServiceStack

How to Check if You Are Affected

To determine whether your application is affected by CVE-2020-28042, inspect your project dependencies for ServiceStack:

inspect dependencies for ServiceStack

Analyze the terminal output to locate any version of ServiceStack in your dependency tree. If any resolved version matches the vulnerable ranges listed in the table below (for example, versions earlier than 5.9.2), 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-347: Improper Verification of Cryptographic Signature, where the product does not verify, or incorrectly verifies, the cryptographic signature for data. In ServiceStack, 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

ServiceStack before 5.9.2 mishandles JWT signature verification unless an application has a custom ValidateToken function that establishes a valid minimum length for a signature.

CVE-2020-28042 Affected ServiceStack Versions

1 component(s)
Fixed Versions:
5.9.2
Product / Package Ecosystem Affected Versions Fixed Version
ServiceStack
nuget/ServiceStack
NuGet
< 5.9.2
5.9.2

References

NVD — CVE-2020-28042 NVD
https://nvd.nist.gov/vuln/detail/CVE-2020-28042
Security Fix Commit FIX COMMIT
https://github.com/ServiceStack/ServiceStack/commit/540d4060e877a03ae95343c1a8560a26768585ee
ServiceStack Release RELEASE
https://forums.servicestack.net/t/servicestack-v5-9-2-released/8850
snyk.io/vuln/snyk-dotnet-se... WEB
https://snyk.io/vuln/SNYK-DOTNET-SERVICESTACK-1035519
www.nuget.org/packages/servicesta... WEB
https://www.nuget.org/packages/ServiceStack
www.shielder.it/advisories/services... WEB
https://www.shielder.it/advisories/servicestack-jwt-signature-verification-bypass
www.shielder.it/blog/2020/11/re-dis... WEB
https://www.shielder.it/blog/2020/11/re-discovering-a-jwt-authentication-bypass-in-servicestack

Frequently Asked Questions

What is CVE-2020-28042?
CVE-2020-28042 is a security vulnerability in ServiceStack involving Signature validation bypass in ServiceStack under CWE-347: Improper Verification of Cryptographic Signature.
Which ServiceStack versions are affected?
Affected versions include releases prior to 5.9.2 across affected packages: ServiceStack.
What version fixes CVE-2020-28042?
Upgrading to 5.9.2 (or the latest patched release for your respective branch) resolves the vulnerability.
Is ServiceStack affected?
Yes, ServiceStack is affected in releases prior to 5.9.2. Upgrade your dependency to 5.9.2 or later.
What CWE is associated with CVE-2020-28042?
CVE-2020-28042 is classified under CWE-347: Improper Verification of Cryptographic Signature (The product does not verify, or incorrectly verifies, the cryptographic signature for data.).
How can I check NuGet dependencies for CVE-2020-28042?
Run the dependency tree command: 'inspect dependencies for ServiceStack'. 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-v5rv-hpxg-8x49",
  "modified" : "2021-01-13T19:12:58Z",
  "published" : "2021-01-13T19:13:11Z",
  "aliases" : [ "CVE-2020-28042" ],
  "summary" : "Signature validation bypass in ServiceStack",
  "details" : "ServiceStack before 5.9.2 mishandles JWT signature verification unless an application has a custom ValidateToken function that establishes a valid minimum length for a signature.",
  "severity" : [ ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "NuGet",
      "name" : "ServiceStack"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      }, {
        "fixed" : "5.9.2"
      } ]
    } ]
  } ],
  "references" : [ {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2020-28042"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/ServiceStack/ServiceStack/commit/540d4060e877a03ae95343c1a8560a26768585ee"
  }, {
    "type" : "WEB",
    "url" : "https://forums.servicestack.net/t/servicestack-v5-9-2-released/8850"
  }, {
    "type" : "WEB",
    "url" : "https://snyk.io/vuln/SNYK-DOTNET-SERVICESTACK-1035519"
  }, {
    "type" : "WEB",
    "url" : "https://www.nuget.org/packages/ServiceStack"
  }, {
    "type" : "WEB",
    "url" : "https://www.shielder.it/advisories/servicestack-jwt-signature-verification-bypass"
  }, {
    "type" : "WEB",
    "url" : "https://www.shielder.it/blog/2020/11/re-discovering-a-jwt-authentication-bypass-in-servicestack"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-347" ],
    "severity" : "MODERATE",
    "github_reviewed" : true,
    "github_reviewed_at" : "2021-01-13T19:12:58Z",
    "nvd_published_at" : "2020-11-02T21:15:00Z"
  }
}