CVE-2020-28042

MEDIUM

Servicestack < 5.9.2 - Signature Verification Bypass

Title source: rule

Description

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.

Exploits (1)

nomisec WORKING POC 282 stars

by z-bool · poc

https://github.com/z-bool/Venom-JWT

View Code ZIP pw:eip

References (4)

[Release Notes, Vendor Advisory] https://forums.servicestack.net/t/servicestack-v5-9-2-released/8850

[Patch, Third Party Advisory] https://github.com/ServiceStack/ServiceStack/commit/540d4060e877a03ae95343c1a8560a26768585ee

[Exploit, Third Party Advisory] https://www.shielder.it/advisories/servicestack-jwt-signature-verification-bypass/

[Exploit, Third Party Advisory] https://www.shielder.it/blog/2020/11/re-discovering-a-jwt-authentication-bypass-in-servicestack/

Scores

CVSS v3 5.3

EPSS 0.3599

EPSS Percentile 97.0%

Attack Vector NETWORK

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N

Classification

CWE

CWE-347

Status published

Affected Products (2)

servicestack/servicestack < 5.9.2

nuget/ServiceStack < 5.9.2NuGet

Timeline

Published Nov 02, 2020

Tracked Since Feb 18, 2026