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CVE-2020-28042

21
FAUCET Score

CVE-2020-28042 affects ServiceStack versions prior to 5.9.2, stemming from improper handling of JWT signature verification. This medium-severity vulnerability (CVSS 5.3) allows for low-impact integrity compromise (I:L) without authentication (PR:N) or user interaction (UI:N), provided a custom ValidateToken function isn't implemented with a minimum signature length. There is no evidence of active exploitation, public exploit code, or significant community discussion surrounding this CVE.

Impacted Technologies

VendorProductVersion(s)CPE
< 5.9.2CPE matchmatch criteria
cpe:2.3:a:servicestack:servicestack:*:*:*:*:*:*:*:*

CVSS Data

CVSS version used by this source: 3.1

5.3MEDIUM

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

Attack Vector
NETWORK
Attack Complexity
LOW
Privileges Required
NONE
User Interaction
NONE
Scope
UNCHANGED
Confidentiality Impact
NONE
Integrity Impact
LOW
Availability Impact
NONE
Exploitability Score
3.9
Impact Score
1.4
CvssVersion
3.1

Exploit Intelligence

EPSS Score
2.33%
Probability of exploitation in next 30 days
EPSS Percentile
81.7%
Percentile rank of EPSS score among Peer Group
As of 2026-07-25
Model: v2026.06.15
This CVE's current EPSS score of 0.0232 is in the 72nd percentile among its peer group of 23,701 CVEs.

Social Chatter

The average CVE in this peer group has 0.0 Twitter, 0.0 Reddit, 0.1 Bluesky, 0.0 Mastodon, and 0.4 GitHub mentions.

Media Mentions

No media coverage found for this CVE.

The average CVE in this peer group has 0.0 InfoSec Media, 0.0 Vendor Blog, and 0.0 Security Researcher mentions.

Remediation

Patch Available

Vendor Patches (2)

github_advisorypatch availablevia nvd_reference
View patch
nugetpatch availablevia ghsa
Product: ServiceStackFixed in: 5.9.2

Vendor Advisories (1)

nugetGHSA-v5rv-hpxg-8x49medium

Signature validation bypass in ServiceStack

Jan 13, 2021

References

forums.servicestack.net / t/servicestack-v5-9-2-released/8850
Release NotesVendor Advisory
github.com / ServiceStack/ServiceStack/commit/540d4060e877a03ae95343c1a8560a26768585ee
PatchThird Party Advisory
shielder.it / advisories/servicestack-jwt-signature-verification-bypass
ExploitThird Party Advisory
shielder.it / blog/2020/11/re-discovering-a-jwt-authentication-bypass-in-servicestack
ExploitThird Party Advisory