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Vulnerability · Published Mar 17, 2026 · Assigned by VulDB

CVE-2026-4349Duende IdentityServer4 Token Renewal Endpoint authorize improper authentication

Medium 5.6

In plain English

A medium-severity improper authentication in IdentityServer4 from Duende. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.4% (higher than 38% of all known vulnerabilities).

Severity (CVSS 3.1)5.6Medium
Exploit odds (30 days)0.4%top 62.3% of all CVEs
Exploited in the wildNo reportsCISA SSVC: none
Attack toolingNoneno public tooling known

Official 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.

Affected products (as reported)

VendorProductVersions
Duende IdentityServer4 4.1.04.1.14.1.2

Weakness: CWE-287 · Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:L/E:X/RL:X/RC:X

References