GHSA-HQP7-G6VH-8MF8
Vulnerability from github – Published: 2026-10-06 09:31 – Updated: 2026-10-06 09:31Improper authentication (CWE-287) in the OAuth token endpoint in Cloud Foundry UAA allows a remote, authenticated attacker holding a valid user access token to obtain a fully-privileged client_credentials token for the OAuth client that issued it, by presenting the user token as an OAuth 2.0 Bearer credential on a client_credentials grant request in place of the client’s configured secret.
UAA’s client_credentials handling does not verify that the Bearer credential supplied for client authentication is actually a client credential (a client secret or a valid configured client authentication method); it accepts any valid access token whose client_id matches the request. A token obtained by a normal end user through a public authorization_code + PKCE flow — scoped only to uaa.user, carrying a user_id, and recording client_auth_method=none — satisfies this check. That user token cannot itself administer OAuth clients (POST /oauth/clients correctly returns 403), but when replayed as Bearer authentication on a client_credentials request for the same client, UAA issues a new client-only token carrying the client’s full authorities, such as clients.write. An attacker can use that token to create arbitrary new OAuth clients, including clients with attacker-chosen authorities, without ever possessing the client’s actual secret.
Exploitation requires a valid user access token (the attacker’s own) for a client that is configured to support both a public, user-facing authorization flow and the client_credentials grant type on the same client_id — a non-default combination. Practical impact scales with the authorities assigned to that client.
{
"affected": [],
"aliases": [
"CVE-2026-59358"
],
"database_specific": {
"cwe_ids": [
"CWE-287"
],
"github_reviewed": false,
"github_reviewed_at": null,
"nvd_published_at": "2026-10-06T07:16:59Z",
"severity": "HIGH"
},
"details": "Improper authentication (CWE-287) in the OAuth token endpoint in Cloud Foundry UAA allows a remote, authenticated attacker holding a valid user access token to obtain a fully-privileged client_credentials token for the OAuth client that issued it, by presenting the user token as an OAuth 2.0 Bearer credential on a client_credentials grant request in place of the client\u2019s configured secret.\n\n\n\nUAA\u2019s client_credentials handling does not verify that the Bearer credential supplied for client authentication is actually a client credential (a client secret or a valid configured client authentication method); it accepts any valid access token whose client_id matches the request. A token obtained by a normal end user through a public authorization_code + PKCE flow \u2014 scoped only to uaa.user, carrying a user_id, and recording client_auth_method=none \u2014 satisfies this check. That user token cannot itself administer OAuth clients (POST /oauth/clients correctly returns 403), but when replayed as Bearer authentication on a client_credentials request for the same client, UAA issues a new client-only token carrying the client\u2019s full authorities, such as clients.write. An attacker can use that token to create arbitrary new OAuth clients, including clients with attacker-chosen authorities, without ever possessing the client\u2019s actual secret.\n\n\n\nExploitation requires a valid user access token (the attacker\u2019s own) for a client that is configured to support both a public, user-facing authorization flow and the client_credentials grant type on the same client_id \u2014 a non-default combination. Practical impact scales with the authorities assigned to that client.",
"id": "GHSA-hqp7-g6vh-8mf8",
"modified": "2026-10-06T09:31:23Z",
"published": "2026-10-06T09:31:23Z",
"references": [
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2026-59358"
},
{
"type": "WEB",
"url": "https://www.cloudfoundry.org/blog/cve-2026-59358-uaa-oauth-token-endpoint-vulnerability-allows-user-access-token-reuse-for-client_credentials-grant-type"
}
],
"schema_version": "1.4.0",
"severity": [
{
"score": "CVSS:4.0/AV:N/AC:L/AT:P/PR:L/UI:N/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X",
"type": "CVSS_V4"
}
]
}
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