---
cve: "CVE-2026-37977"
severity: "LOW"
cvss: 3.7
epss: "25%"
vendor: "Red Hat"
kev: false
exploited: false
published: "2026-04-06 09:16:17"
tags: [cve, security, low]
source: tsecurity.de CVE-Dossier
exported: "2026-09-17T08:24:45+02:00"
---

# CVE-2026-37977

> 3.7 LOW

## Beschreibung

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: ["*"]`.

## CVSS-Vektor

```
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:N/A:N
```

| Metrik | Wert | Bewertung |
|---|---|---|
| AV Angriffsvektor | Netzwerk | bad |
| AC Komplexität | Hoch | good |
| PR Privilegien | Keine | bad |
| UI Interaktion | Keine | bad |
| S Scope | Unverändert | good |
| C Vertraulichkeit | Gering | warn |
| I Integrität | Keine | good |
| A Verfügbarkeit | Keine | good |

## Referenzen

- <https://access.redhat.com/errata/RHSA-2026:25097>
- <https://access.redhat.com/errata/RHSA-2026:25098>
- <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>

---
_Exportiert aus dem [tsecurity.de CVE-Dossier](https://tsecurity.de/cve?cve=CVE-2026-37977) · Datenquellen: EUVD (ENISA), NVD, OSV, CISA KEV, FIRST EPSS, Exploit-DB, BSI BITS_