Vulnerability from bitnami_vulndb
Published
2026-08-31 14:36
Modified
2026-09-17 12:08
Summary
Keycloak-services: keycloak-services: required signed-jwt assertion policy can be bypassed with unsigned assertion headers
Details

Keycloak provides a mechanism called Client Policies to enforce security requirements on clients, such as requiring them to use signed JWTs for authentication. A flaw was discovered where this enforcement can be bypassed. An attacker with valid client credentials can provide a fake, unsigned assertion header that tricks the system into thinking the policy requirements have been met. This allows the attacker to authenticate using simpler methods like a client secret even when the administrator has mandated more secure, signed assertions.

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{
  "affected": [
    {
      "package": {
        "ecosystem": "Bitnami",
        "name": "keycloak",
        "purl": "pkg:bitnami/keycloak"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "26.7.3"
            }
          ],
          "type": "SEMVER"
        }
      ],
      "severity": [
        {
          "score": "CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:L/A:N",
          "type": "CVSS_V3"
        }
      ]
    }
  ],
  "aliases": [
    "CVE-2026-16093"
  ],
  "database_specific": {
    "cpes": [
      "cpe:2.3:a:redhat:build_of_keycloak:*:*:*:*:-:*:*:*",
      "cpe:2.3:a:keycloak:keycloak:*:*:*:*:*:*:*:*"
    ],
    "severity": "Medium"
  },
  "details": "Keycloak provides a mechanism called Client Policies to enforce security requirements on clients, such as requiring them to use signed JWTs for authentication. A flaw was discovered where this enforcement can be bypassed. An attacker with valid client credentials can provide a fake, unsigned assertion header that tricks the system into thinking the policy requirements have been met. This allows the attacker to authenticate using simpler methods like a client secret even when the administrator has mandated more secure, signed assertions.",
  "id": "BIT-keycloak-2026-16093",
  "modified": "2026-09-17T12:08:03.261Z",
  "published": "2026-08-31T14:36:55.423Z",
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://access.redhat.com/security/cve/CVE-2026-16093"
    },
    {
      "type": "ADVISORY",
      "url": "https://bugzilla.redhat.com/show_bug.cgi?id=2501729"
    },
    {
      "type": "WEB",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-16093"
    },
    {
      "type": "WEB",
      "url": "https://access.redhat.com/errata/RHSA-2026:68277"
    },
    {
      "type": "WEB",
      "url": "https://access.redhat.com/errata/RHSA-2026:68278"
    }
  ],
  "schema_version": "1.6.2",
  "summary": "Keycloak-services: keycloak-services: required signed-jwt assertion policy can be bypassed with unsigned assertion headers"
}



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