What’s Vulnerable › Vulnerabilities

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

• Severity: medium (CVSS 5.6 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.4% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2026-03-17 · updated 2026-06-17
• Weakness: CWE-287

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

• Duende IdentityServer4: 4.1.0, 4.1.1, 4.1.2

References

• https://vuldb.com/?ctiid.351380
• https://vuldb.com/?id.351380
• https://vuldb.com/?submit.772071

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