CVE-2026-4349
Duende IdentityServer4 Token Renewal Endpoint authorize improper authentication
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.
Attack profile
How easy it is to exploit
- Attack vector
- Network
- Complexity
- High
- Privileges needed
- None
- User interaction
- None
What an attacker can affect
- Confidentiality
- Low
- Integrity
- Low
- Availability
- Low
Exploit likelihood
What each source reports
CVE List Score used
Duende IdentityServer4 Token Renewal Endpoint authorize improper authentication
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.
- Record
CVE-2026-4349- CVSS 4.0
- 6.3 Medium
CVSS:4.0/AV:N/AC:H/AT:N/PR:N/UI:N/VC:L/VI:L/VA:L/SC:N/SI:N/SA:N/E:X - CVSS 3.1
- 5.6 Medium
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 - CVSS 3.0
- 5.6 Medium
CVSS:3.0/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:L/E:X/RL:X/RC:X - CVSS 2.0
- 5.1
AV:N/AC:H/Au:N/C:P/I:P/A:P/E:ND/RL:ND/RC:ND - Weakness
- CWE-287
- Updated
- 2026-11-02
EUVDEUVD-2026-12659
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.
- Record
EUVD-2026-12659- CVSS 4.0
- 6.3 Medium
CVSS:4.0/AV:N/AC:H/AT:N/PR:N/UI:N/VC:L/VI:L/VA:L/SC:N/SI:N/SA:N/E:X - Updated
- 2026-11-02
GitHub AdvisoriesGHSA-46qm-5mvh-mmxr
A vulnerability was determined in Duende IdentityServer 4. The affected element is an unknown...
A vulnerability was determined in Duende IdentityServer 4. 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. The vendor was contacted early about this disclosure but did not respond in any way.
- Record
GHSA-46qm-5mvh-mmxr- CVSS 4.0
- 6.3 Medium
CVSS:4.0/AV:N/AC:H/AT:N/PR:N/UI:N/VC:L/VI:L/VA:L/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X - CVSS 3.1
- 5.6 Medium
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:L - Weakness
- CWE-287
- Updated
- 2026-11-02
NVD
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.
- Record
CVE-2026-4349- CVSS 4.0
- 6.3 Medium
CVSS:4.0/AV:N/AC:H/AT:N/PR:N/UI:N/VC:L/VI:L/VA:L/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X - CVSS 3.1
- 5.6 Medium
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:L - CVSS 2.0
- 5.1 Medium
AV:N/AC:H/Au:N/C:P/I:P/A:P - Weakness
- CWE-287
- Updated
- 2026-11-02
Affected products
History
| Recorded | Changed | Sources |
|---|---|---|
| first indexed | CVE List, EUVD, GitHub Advisories, NVD |
Dates are when Every CVE recorded each change. Upstream dates may differ.
In short
CVE-2026-4349 is a medium vulnerability (CVSS 6.3) in Duende Identityserver4, published March 17, 2026. No source lists public exploit code. EPSS puts the chance of exploitation in the next 30 days at 0.43%, the 37th percentile. No source names a fixed version.