PT-2020-16905 · Servicestack · Servicestack

Published 2020-03-11 · Updated 2021-01-13 · CVE-2020-28042

Positive Technologies (AI Summary)

CVSS v3.1

5.3

Medium

Base vector

AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N

Name of the Vulnerable Software and Affected Versions ServiceStack versions prior to 5.9.2

Description The issue is related to the mishandling of JWT signature verification. This occurs unless an application has a custom ValidateToken function that establishes a valid minimum length for a signature.

Recommendations For versions prior to 5.9.2, update to version 5.9.2 or later to resolve the issue. As a temporary workaround, consider implementing a custom ValidateToken function that establishes a valid minimum length for a signature to mitigate the risk of exploitation.

Exploit

Fix

Improper Verification of Cryptographic Signature

Weakness Enumeration

CWE-347

Related Identifiers

BDU:2025-03227

CVE-2020-28042

GHSA-V5RV-HPXG-8X49

Affected Products

Servicestack

References · 12

• 🔥 https://shielder.it/advisories/servicestack-jwt-signature-verification-bypass · Exploit
• 🔥 https://shielder.it/blog/2020/11/re-discovering-a-jwt-authentication-bypass-in-servicestack · Exploit
• https://github.com/ServiceStack/ServiceStack/commit/540d4060e877a03ae95343c1a8560a26768585ee · Patch
• https://forums.servicestack.net/t/servicestack-v5-9-2-released/8850 · Vendor Advisory
• https://osv.dev/vulnerability/CVE-2020-28042 · Vendor Advisory
• https://nvd.nist.gov/vuln/detail/CVE-2020-28042 · Security Note
• https://osv.dev/vulnerability/GHSA-v5rv-hpxg-8x49 · Vendor Advisory
• https://bdu.fstec.ru/vul/2025-03227 · Security Note
• https://t.me/cvenotify/5715 · Telegram Post
• https://nuget.org/packages/ServiceStack · Note
• https://t.me/cvenotify/5114 · Telegram Post
• https://snyk.io/vuln/SNYK-DOTNET-SERVICESTACK-1035519 · Note