CVE-2026-4349
CVE-2026-4349 is a medium-severity vulnerability with a CVSS 3.x base score of 5.6. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-287.
Key facts
- Severity: Medium (CVSS 3.x base score 5.6)
- CVSS v2: 5.1
- CVSS v4: 6.3
- EPSS exploit prediction: 0% (33rd percentile)
- Actively exploited: Not listed in CISA KEV
- EU (EUVD) id: EUVD-2026-12659
- Weakness: CWE-287
- Published:
- Last modified:
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.
Frequently asked questions
- What is CVE-2026-4349?
- 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.
- How severe is CVE-2026-4349?
- CVE-2026-4349 has a CVSS 3.x base score of 5.6, rated medium severity. It is exploitable over network with high attack complexity, requires no privileges and no user interaction. Impact on confidentiality is low, integrity low, and availability low.
- Is CVE-2026-4349 being actively exploited?
- It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (33rd percentile), an estimate of the probability of exploitation in the next 30 days.
- How do I fix CVE-2026-4349?
- Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.
- Does CVE-2026-4349 have an EU (EUVD) identifier?
- Yes. CVE-2026-4349 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-12659.
- When was CVE-2026-4349 published?
- CVE-2026-4349 was published on 2026-03-17 and last updated on 2026-06-17.
References
Other CWE-287 (Improper Authentication) vulnerabilities
- CVE-2026-45480 — Critical (CVSS 10.0): Improper authentication in Azure Active Directory allows an unauthorized attacker to elevate privileges over a network.
- CVE-2026-46389 — Critical (CVSS 10.0): UDS Identity Config builds the Keycloak configuration image (realm, plugins, theme, truststore, JARs) consumed by UDS…
- CVE-2026-10611 — Critical (CVSS 10.0): An authentication bypass vulnerability exists in MISP when LDAP mixed authentication is enabled with OTP enforcement.…
- CVE-2026-47280 — Critical (CVSS 10.0): Improper authentication in Azure Resource Manager (ARM) allows an unauthorized attacker to elevate privileges over a…
- CVE-2026-42822 — Critical (CVSS 10.0): Improper authentication in Azure Local Disconnected Operations allows an unauthorized attacker to elevate privileges…
- CVE-2026-20182 — Critical (CVSS 10.0): May 2026: This security advisory provides the details and fix information for a vulnerability that was discovered and…
Browse all CWE-287 (Improper Authentication) vulnerabilities →