Advisory details:
vulnrichment / CVE-2026-37977
| Advisory ID | vulnrichment/CVE-2026-37977 |
| Aliases | |
| Summary | 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: ["*"]`. |
| Status | Published |
| Exploitability | 0.5 |
| Weighted Severity | 0.0 |
| Risk | |
| Affected and Fixed Packages | Package Details |
| Introduced and Fixed Package Commit Patches | Package Commit Patches Details |
| CWE-346 | Origin Validation Error |
| System | Score | Found at |
|---|---|---|
| cvssv3.1 | 3.7 | |
| ssvc | Track |
| Reference id | Reference type | URL |
|---|---|---|
| https://access.redhat.com/errata/RHSA-2026:30049 | ||
| https://access.redhat.com/errata/RHSA-2026:30050 | ||
| https://access.redhat.com/security/cve/CVE-2026-37977 | ||
| https://bugzilla.redhat.com/show_bug.cgi?id=2455324 | ||
| cpe:/a:redhat:build_keycloak:26.4::el9 | Other | https://nvd.nist.gov/vuln/search/results?adv_search=true&isCpeNameSearch=true&query=cpe:/a:redhat:build_keycloak:26.4::el9 |
| cpe:/a:redhat:build_keycloak:26.6::el9 | Other | https://nvd.nist.gov/vuln/search/results?adv_search=true&isCpeNameSearch=true&query=cpe:/a:redhat:build_keycloak:26.6::el9 |
| RHSA-2026:25097 | Advisory | https://access.redhat.com/errata/RHSA-2026:25097 |
| RHSA-2026:25098 | Advisory | https://access.redhat.com/errata/RHSA-2026:25098 |
No EPSS data available for this advisory.
| Patch URL | |
|---|---|
| There are no known patches. | |
| Attack Vector (AV) | Attack Complexity (AC) | Privileges Required (PR) | User Interaction (UI) | Scope (S) | Confidentiality Impact (C) | Integrity Impact (I) | Availability Impact (A) |
|---|---|---|---|---|---|---|---|
network adjacent_network local physical |
low high |
none low high |
none required |
unchanged changed |
high low none |
high low none |
high low none |
Vector: SSVCv2/E:N/A:N/T:P/P:M/B:A/M:M/D:T/2026-04-06T11:55:21Z/
Decision: Track
Source URL: https://github.com/cisagov/vulnrichment/blob/develop/2026/37xxx/CVE-2026-37977.json
Source Advisory: vulnrichment/CVE-2026-37977
[{'Exploitation': 'none'},
{'Automatable': 'no'},
{'Technical Impact': 'partial'},
{'Mission Prevalence': 'minimal'},
{'Public Well-being Impact': 'material'},
{'Mission & Well-being': 'medium'}]