CVE-2026-37977 | Keycloak on Red Hat JWT azp origin validation (EUVD-2026-19201)

VDB-355502 · CVE-2026-37977 · EUVD-2026-19201 KEYCLOAK ON RED HAT JWT AZP ORIGIN VALIDATION HISTORYDIFFRELATEJSONXMLCTI CVSS Meta Temp Score Current Exploit Price (≈) CTI Interest Score 3.7 $0-$5k 1.83+ Summaryinfo A vulnerability classified as problematic was found in Keycloak on Red Hat. This issue affects some unknown processing of the component JWT Handler. Such manipulation of the argument azp leads to origin validation. This vulnerability is uniquely identified as CVE-2026-37977. The attack can be launched remotely. No exploit exists. Detailsinfo A vulnerability, which was classified as problematic, has been found in Keycloak on Red Hat (version unknown). Affected by this issue is an unknown function of the component JWT Handler. The manipulation of the argument azp with an unknown input leads to a origin validation vulnerability. Using CWE to declare the problem leads to CWE-346. The product does not properly verify that the source of data or communication is valid. Impacted is confidentiality. CVE summarizes: A flaw was found in Keycloak. A remote attacker can exploit a Cross-Origin Resource Sharing (CORS) header injection vulnerability in Keycloak's User-Managed Access (UMA) token endpoint. This flaw occurs because the `azp` claim from a client-supplied JSON Web Token (JWT) is used to set the `Access-Control-Allow-Origin` header before the JWT signature is validated. When a specially crafted JWT with an attacker-controlled `azp` value is processed, this value is reflected as the CORS origin, even if the grant is later rejected. This can lead to the exposure of low-sensitivity information from authorization server error responses, weakening origin isolation, but only when a target client is misconfigured with `webOrigins: ["*"]`. The advisory is available at access.redhat.com. This vulnerability is handled as CVE-2026-37977 since 04/06/2026. The exploitation is known to be difficult. The attack may be launched remotely. No form of authentication is required for exploitation. Technical details are known, but there is no available exploit. The structure of the vulnerability defines a possible price range of USD $0-$5k at the moment (estimation calculated on 04/06/2026). There is no information about possible countermeasures known. It may be suggested to replace the affected object with an alternative product. The vulnerability is also documented in the vulnerability database at EUVD (EUVD-2026-19201). Productinfo Name Keycloak License open-source CPE 2.3info 🔒 CPE 2.2info 🔒 CVSSv4info VulDB Vector: 🔒 VulDB Reliability: 🔍 CVSSv3info VulDB Meta Base Score: 3.7 VulDB Meta Temp Score: 3.7 VulDB Base Score: 3.7 VulDB Temp Score: 3.7 VulDB Vector: 🔒 VulDB Reliability: 🔍 CNA Base Score: 3.7 CNA Vector (redhat): 🔒 CVSSv2info Vector Complexity Authentication Confidentiality Integrity Availability Unlock Unlock Unlock Unlock Unlock Unlock Unlock Unlock Unlock Unlock Unlock Unlock Unlock Unlock Unlock Unlock Unlock Unlock VulDB Base Score: 🔒 VulDB Temp Score: 🔒 VulDB Reliability: 🔍 Exploitinginfo Class: Origin validation CWE: CWE-346 / CWE-345 CAPEC: 🔒 ATT&CK: 🔒 Physical: No Local: No Remote: Yes Availability: 🔒 Status: Not defined Price Prediction: 🔍 Current Price Estimation: 🔒 0-Day Unlock Unlock Unlock Unlock Today Unlock Unlock Unlock Unlock Threat Intelligenceinfo Interest: 🔍 Active Actors: 🔍 Active APT Groups: 🔍 Countermeasuresinfo Recommended: no mitigation known Status: 🔍 0-Day Time: 🔒 Timelineinfo 04/06/2026 Advisory disclosed 04/06/2026 +0 days CVE reserved 04/06/2026 +0 days VulDB entry created 04/06/2026 +0 days VulDB entry last update Sourcesinfo Advisory: access.redhat.com Status: Confirmed CVE: CVE-2026-37977 (🔒) GCVE (CVE): GCVE-0-2026-37977 GCVE (VulDB): GCVE-100-355502 EUVD: 🔒 Entryinfo Created: 04/06/2026 11:39 Updated: 04/06/2026 12:30 Changes: 04/06/2026 11:39 (61), 04/06/2026 12:30 (1) Complete: 🔍 Cache ID: 99:B82:101 Discussion No comments yet. Languages: en. Please log in to comment. ◂ PreviousOverviewNext ▸