{"dataType": "CVE_RECORD", "dataVersion": "5.2", "cveMetadata": {"cveId": "CVE-2026-37977", "assignerOrgId": "53f830b8-0a3f-465b-8143-3b8a9948e749", "state": "PUBLISHED", "assignerShortName": "redhat", "dateReserved": "2026-04-06T07:48:39.721Z", "datePublished": "2026-04-06T08:38:36.657Z", "dateUpdated": "2026-04-24T15:44:23.520Z"}, "containers": {"cna": {"title": "Keycloak: org.keycloak.protocol.oidc.grants.ciba: keycloak: information disclosure via cors header injection due to unvalidated jwt azp claim", "metrics": [{"other": {"content": {"value": "Low", "namespace": "https://access.redhat.com/security/updates/classification/"}, "type": "Red Hat severity rating"}}, {"cvssV3_1": {"attackComplexity": "HIGH", "attackVector": "NETWORK", "availabilityImpact": "NONE", "baseScore": 3.7, "baseSeverity": "LOW", "confidentialityImpact": "LOW", "integrityImpact": "NONE", "privilegesRequired": "NONE", "scope": "UNCHANGED", "userInteraction": "NONE", "vectorString": "CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:N/A:N", "version": "3.1"}, "format": "CVSS"}], "descriptions": [{"lang": "en", "value": "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: [\"*\"]`."}], "affected": [{"vendor": "Red Hat", "product": "Red Hat Build of Keycloak", "collectionURL": "https://access.redhat.com/downloads/content/package-browser/", "packageName": "rhbk/keycloak-rhel9", "defaultStatus": "affected", "cpes": ["cpe:/a:redhat:build_keycloak:"]}], "references": [{"url": "https://access.redhat.com/security/cve/CVE-2026-37977", "tags": ["vdb-entry", "x_refsource_REDHAT"]}, {"url": "https://bugzilla.redhat.com/show_bug.cgi?id=2455324", "name": "RHBZ#2455324", "tags": ["issue-tracking", "x_refsource_REDHAT"]}], "datePublic": "2026-04-06T08:34:01.137Z", "problemTypes": [{"descriptions": [{"cweId": "CWE-346", "description": "Origin Validation Error", "lang": "en", "type": "CWE"}]}], "x_redhatCweChain": "CWE-346: Origin Validation Error", "timeline": [{"lang": "en", "time": "2026-04-06T07:49:33.467Z", "value": "Reported to Red Hat."}, {"lang": "en", "time": "2026-04-06T08:34:01.137Z", "value": "Made public."}], "providerMetadata": {"orgId": "53f830b8-0a3f-465b-8143-3b8a9948e749", "shortName": "redhat", "dateUpdated": "2026-04-24T15:44:23.520Z"}, "x_generator": {"engine": "cvelib 1.8.0"}}, "adp": [{"metrics": [{"other": {"type": "ssvc", "content": {"timestamp": "2026-04-06T11:55:21.318112Z", "id": "CVE-2026-37977", "options": [{"Exploitation": "none"}, {"Automatable": "no"}, {"Technical Impact": "partial"}], "role": "CISA Coordinator", "version": "2.0.3"}}}], "title": "CISA ADP Vulnrichment", "providerMetadata": {"orgId": "134c704f-9b21-4f2e-91b3-4a467353bcc0", "shortName": "CISA-ADP", "dateUpdated": "2026-04-06T11:57:17.383Z"}}]}}

{"dataType": "CVE_RECORD", "containers": {"adp": [{"title": "CISA ADP Vulnrichment", "metrics": [{"other": {"type": "ssvc", "content": {"id": "CVE-2026-37977", "role": "CISA Coordinator", "options": [{"Exploitation": "none"}, {"Automatable": "no"}, {"Technical Impact": "partial"}], "version": "2.0.3", "timestamp": "2026-04-06T11:55:21.318112Z"}}}], "providerMetadata": {"orgId": "134c704f-9b21-4f2e-91b3-4a467353bcc0", "shortName": "CISA-ADP", "dateUpdated": "2026-04-06T11:57:12.995Z"}}], "cna": {"title": "Keycloak: org.keycloak.protocol.oidc.grants.ciba: keycloak: information disclosure via cors header injection due to unvalidated jwt azp claim", "metrics": [{"other": {"type": "Red Hat severity rating", "content": {"value": "Low", "namespace": "https://access.redhat.com/security/updates/classification/"}}}, {"format": "CVSS", "cvssV3_1": {"scope": "UNCHANGED", "version": "3.1", "baseScore": 3.7, "attackVector": "NETWORK", "baseSeverity": "LOW", "vectorString": "CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:N/A:N", "integrityImpact": "NONE", "userInteraction": "NONE", "attackComplexity": "HIGH", "availabilityImpact": "NONE", "privilegesRequired": "NONE", "confidentialityImpact": "LOW"}}], "affected": [{"cpes": ["cpe:/a:redhat:build_keycloak:"], "vendor": "Red Hat", "product": "Red Hat Build of Keycloak", "packageName": "rhbk/keycloak-rhel9", "collectionURL": "https://access.redhat.com/downloads/content/package-browser/", "defaultStatus": "affected"}], "timeline": [{"lang": "en", "time": "2026-04-06T07:49:33.467Z", "value": "Reported to Red Hat."}, {"lang": "en", "time": "2026-04-06T08:34:01.137Z", "value": "Made public."}], "datePublic": "2026-04-06T08:34:01.137Z", "references": [{"url": "https://access.redhat.com/security/cve/CVE-2026-37977", "tags": ["vdb-entry", "x_refsource_REDHAT"]}, {"url": "https://bugzilla.redhat.com/show_bug.cgi?id=2455324", "name": "RHBZ#2455324", "tags": ["issue-tracking", "x_refsource_REDHAT"]}], "x_generator": {"engine": "cvelib 1.8.0"}, "descriptions": [{"lang": "en", "value": "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: [\"*\"]`."}], "problemTypes": [{"descriptions": [{"lang": "en", "type": "CWE", "cweId": "CWE-346", "description": "Origin Validation Error"}]}], "providerMetadata": {"orgId": "53f830b8-0a3f-465b-8143-3b8a9948e749", "shortName": "redhat", "dateUpdated": "2026-04-24T15:44:23.520Z"}, "x_redhatCweChain": "CWE-346: Origin Validation Error"}}, "cveMetadata": {"cveId": "CVE-2026-37977", "state": "PUBLISHED", "dateUpdated": "2026-04-24T15:44:23.520Z", "dateReserved": "2026-04-06T07:48:39.721Z", "assignerOrgId": "53f830b8-0a3f-465b-8143-3b8a9948e749", "datePublished": "2026-04-06T08:38:36.657Z", "assignerShortName": "redhat"}, "dataVersion": "5.2"}

{"configurations": [{"nodes": [{"cpeMatch": [{"criteria": "cpe:2.3:a:redhat:build_of_keycloak:-:*:*:*:-:*:*:*", "matchCriteriaId": "E5C930CB-4EAD-497B-A44B-D880F2A1F85B", "vulnerable": true}], "negate": false, "operator": "OR"}]}], "cveTags": [], "descriptions": [{"lang": "en", "value": "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: [\"*\"]`."}], "id": "CVE-2026-37977", "lastModified": "2026-04-24T15:39:21.883", "metrics": {"cvssMetricV31": [{"cvssData": {"attackComplexity": "HIGH", "attackVector": "NETWORK", "availabilityImpact": "NONE", "baseScore": 3.7, "baseSeverity": "LOW", "confidentialityImpact": "LOW", "integrityImpact": "NONE", "privilegesRequired": "NONE", "scope": "UNCHANGED", "userInteraction": "NONE", "vectorString": "CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:N/A:N", "version": "3.1"}, "exploitabilityScore": 2.2, "impactScore": 1.4, "source": "secalert@redhat.com", "type": "Secondary"}, {"cvssData": {"attackComplexity": "LOW", "attackVector": "NETWORK", "availabilityImpact": "NONE", "baseScore": 5.3, "baseSeverity": "MEDIUM", "confidentialityImpact": "LOW", "integrityImpact": "NONE", "privilegesRequired": "NONE", "scope": "UNCHANGED", "userInteraction": "NONE", "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N", "version": "3.1"}, "exploitabilityScore": 3.9, "impactScore": 1.4, "source": "nvd@nist.gov", "type": "Primary"}]}, "published": "2026-04-06T09:16:17.850", "references": [{"source": "secalert@redhat.com", "tags": ["Vendor Advisory"], "url": "https://access.redhat.com/security/cve/CVE-2026-37977"}, {"source": "secalert@redhat.com", "tags": ["Issue Tracking", "Vendor Advisory"], "url": "https://bugzilla.redhat.com/show_bug.cgi?id=2455324"}], "sourceIdentifier": "secalert@redhat.com", "vulnStatus": "Analyzed", "weaknesses": [{"description": [{"lang": "en", "value": "CWE-346"}], "source": "secalert@redhat.com", "type": "Primary"}]}

{"bugzilla": {"description": "keycloak: org.keycloak.protocol.oidc.grants.ciba: Keycloak: Information disclosure via CORS header injection due to unvalidated JWT azp claim", "id": "2455324", "url": "https://bugzilla.redhat.com/show_bug.cgi?id=2455324"}, "csaw": false, "cvss3": {"cvss3_base_score": "3.7", "cvss3_scoring_vector": "CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:N/A:N", "status": "draft"}, "cwe": "CWE-346", "details": ["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: [\"*\"]`."], "name": "CVE-2026-37977", "package_state": [{"cpe": "cpe:/a:redhat:build_keycloak:", "fix_state": "Fix deferred", "package_name": "rhbk/keycloak-rhel9", "product_name": "Red Hat Build of Keycloak"}], "public_date": "2026-04-06T08:34:01Z", "references": ["https://www.cve.org/CVERecord?id=CVE-2026-37977\nhttps://nvd.nist.gov/vuln/detail/CVE-2026-37977"], "statement": "Low impact: This vulnerability in Keycloak's UMA token endpoint allows for CORS header injection when a client is misconfigured with `webOrigins: [\"*\"]`. This can lead to the exposure of low-sensitivity information from authorization server error responses. Exploitation requires a specific client misconfiguration and does not affect default Keycloak installations.", "threat_severity": "Low"}

{"affected": [{"configurations": [{"platform": null, "status": "affected", "versions": null}], "enrichment": {"confidence": 95.0, "confidence_source": "inferred", "scores": [{"score": 95.0, "source": "inferred"}, {"score": 98.0, "source": "matching"}]}, "original": {"product": "Red Hat Build of Keycloak", "source": "cna", "vendor": "Red Hat"}, "product": "build_of_keycloak", "vendor": "redhat"}], "analysis": {"en": {"generated_at": "2026-04-06T11:21:43.931765+00:00", "value": {"mitigation_remediation": ["Update Keycloak to the latest version that includes a patch for the CORS header injection flaw. ", "Reconfigure affected clients to use specific webOrigins rather than '*', limiting header reflection to trusted origins. ", "Monitor application logs for unexpected CORS headers or error responses that may indicate an attempted exploit."], "summary": {"action": "Apply Patch", "impact": "Information Disclosure via CORS header injection"}, "threat_synthesis": {"affected_systems": "The vulnerability affects Red Hat Build of Keycloak. No specific version range is listed in the available data, so all installations that have not yet applied a vendor fix are potentially exposed.", "description_and_impact": "A flaw in the User-Managed Access token endpoint of Keycloak allows an attacker to craft a JSON Web Token with a malicious azp claim that is used to set the Access\u2011Control\u2011Allow\u2011Origin header before the token is verified. The header is reflected in the response even if the grant is later rejected, potentially revealing low\u2011sensitivity error information. The underlying weakness is insufficient validation of user input before header generation.", "risk_and_exploitability": "With a CVSS score of 3.7, the vulnerability presents a moderate severity risk. The EPSS score is not available and the issue is not listed in CISA\u2019s KEV catalog, indicating no known widespread exploitation to date. The likely attack vector is remote, requiring the attacker to send a specially crafted JWT to the UMA endpoint of a misconfigured client that permits all web origins. Successful exploitation can compromise origin isolation and disclose error responses, but does not grant arbitrary code execution."}}}}, "created": "2026-04-06T20:14:47.494816+00:00", "updated": "2026-04-06T21:33:05.131224+00:00", "vendors": ["redhat", "redhat$PRODUCT$build_of_keycloak"]}