CVE-2026-4349
Received Received - Intake
Improper Authentication in Duende IdentityServer Token Renewal Endpoint

Publication date: 2026-03-17

Last updated on: 2026-03-25

Assigner: VulDB

Description
A vulnerability was determined in Duende IdentityServer4 up to 4.1.2. The affected element is an unknown function of the file /connect/authorize of the component Token Renewal Endpoint. This manipulation of the argument id_token_hint causes improper authentication. It is possible to initiate the attack remotely. The attack is considered to have high complexity. The exploitability is described as difficult. This vulnerability only affects products that are no longer supported by the maintainer.
CVSS Scores
EPSS Scores
Probability:
Percentile:
Meta Information
Published
2026-03-17
Last Modified
2026-03-25
Generated
2026-06-16
AI Q&A
2026-03-18
EPSS Evaluated
2026-06-15
NVD
CVE-2026-4349
EUVD
EUVD-2026-12659
Affected Vendors & Products
Showing 1 associated CPE
Vendor Product Version / Range
duende identityserver 4
Helpful Resources
Exploitability
CWE
CWE Icon
KEV
KEV Icon
CWE ID Description
CWE-287 When an actor claims to have a given identity, the product does not prove or insufficiently proves that the claim is correct.
Attack-Flow Graph
AI Quick Actions
Instant insights powered by AI
Executive Summary

This vulnerability exists in Duende IdentityServer 4, specifically in an unknown function within the /connect/authorize file related to the Token Renewal Endpoint.

The issue arises from manipulation of the argument id_token_hint, which leads to improper authentication.

An attacker can exploit this vulnerability remotely, but the attack is considered to have high complexity and is difficult to execute.

The vendor was contacted early about this issue but did not respond.

Impact Analysis

This vulnerability can lead to improper authentication, which means an attacker might be able to bypass normal authentication mechanisms.

As a result, unauthorized users could potentially gain access to protected resources or perform actions they should not be allowed to.

The CVSS scores indicate a moderate impact on confidentiality, integrity, and availability.

Compliance Impact

I don't know

Detection Guidance

I don't know

Mitigation Strategies

I don't know

Chat Assistant
Ask questions about this CVE
Hi! I’m here to help you understand CVE-2026-4349. Ask me anything about the vulnerability, its impact, or mitigation strategies.
0/70
EPSS Chart