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CVE Record

CVE-2020-28042: ServiceStack before 5.9.2 mishandles JWT signature verification unless an application has a custom Validate...

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.

UnknownCVSS not scoredNot KEV-listedUpdated
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Glexia's TakeAutomated analysishigh

Security readout for executives and security teams

Plain-English summary

CVE-2020-28042 is an authentication bypass risk in ServiceStack before 5.9.2. Some applications could accept JWTs without properly rejecting invalid or too-short signatures, unless they added custom token validation. For businesses, the concern is unauthorized access to systems that rely on ServiceStack JWT authentication.

Executive priority

Prioritize remediation for internet-facing or sensitive applications using ServiceStack JWT authentication. Even without a CVSS score or KEV listing, authentication bypass can directly affect confidentiality and access control.

Technical view

ServiceStack before 5.9.2 mishandled JWT signature verification when no custom ValidateToken function enforced a valid minimum signature length. The source bundle identifies the issue as a JWT signature verification bypass and points to the 5.9.2 release and fixing commit. No CVSS, CWE, or CPE data is provided.

Likely exposure

Exposure is most likely in applications using ServiceStack JWT authentication on versions before 5.9.2, especially where no custom ValidateToken logic enforces signature length. Systems not using ServiceStack JWT authentication are not shown as affected by the provided sources.

Exploitation context

The Shielder sources describe a JWT authentication bypass, but the bundle does not show CISA KEV listing or confirmed active exploitation. Treat exploitability as plausible for exposed vulnerable applications, while avoiding assumptions about real-world exploitation.

Researcher notes

Evidence is clear on affected pre-5.9.2 ServiceStack JWT behavior, but sparse on product CPEs, CVSS scoring, and exploitation status. Validate exposure by version, JWT usage, and custom ValidateToken behavior before assigning business impact.

Mitigation direction

  • Upgrade ServiceStack to version 5.9.2 or later.
  • Review ServiceStack 5.9.2 release notes and the fixing commit.
  • Confirm any custom ValidateToken logic enforces signature length correctly.
  • Identify applications relying on ServiceStack JWT authentication.
  • Review authentication logs for suspicious JWT-authenticated access.

Validation and detection

  • Inventory deployed ServiceStack versions across applications.
  • Confirm whether JWT authentication is enabled.
  • Check for custom ValidateToken logic and signature length validation.
  • Verify upgraded environments use ServiceStack 5.9.2 or later.
  • Review public routes protected only by JWT authentication.
Prepared
Confidence
medium
Sources
6

Public sources used

Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.

Potential ATT&CK relevance

Conservative CVE-to-ATT&CK context

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CVE-2020-28042 mapping review

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Vulnerability profileCVE Program record
Severity
Unknown
CVSS
Not scored
Known Exploited
No
Published
Official CVE source material

CNA and ADP enrichment extracted from CVE v5

These fields come from the CVE record and ADP containers, not from Glexia's Take. They preserve time-varying source decisions such as CISA SSVC, KEV status, CVSS metrics, and provider references.

0CVSS vectors
0Timeline events
0ADP providers
5Source links

CVSS and timeline data

No CVSS vectors or timeline events were available in the normalized CVE source material.

Source materials

Affected products

Products and packages named in the record

VendorProductVersion / packageStatus
n/an/an/aListed
Weakness

CWE details

No CWE listed

CWE links open Glexia weakness intelligence pages with official CWE context, developer remediation guidance, and related CVE mappings.