Self-UAA OIDC Configuration allows JWT injection to establish unauthorized sessions

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Insufficient verification of data authenticity (CWE-345) in the external OIDC login callback in Cloud Foundry UAA v4.5.0 to v79.6.0 (inclusive) allows an authenticated UAA user to bypass the OAuth authorization-code exchange and establish an authenticated external-OIDC browser session, via submitting a UAA access token or a cross-client ID token as the callback’s id_token parameter. The issue only manifests when a UAA zone is configured with an OIDC identity provider whose issuer exactly matches that zone’s own /oauth/token endpoint (a “self-UAA” OIDC configuration). In this configuration, the callback takes a supplied id_token directly instead of requiring the authorization code exchange, and does not verify that the token was actually issued as an ID token for the specific self-OIDC relying-party client. An attacker holding any valid UAA JWT for themselves — including a plain access token with only uaa.user scope, or a valid ID token issued to an unrelated client such as cf — can present it as the callback’s id_token and be authenticated into a mapped local (“shadow”) account. Because the resulting session is not verified against the originating token’s true audience or user_id, its effective privilege depends entirely on the shadow account’s group memberships, which can include administrative scopes such as clients.write. Exploitation requires a valid UAA user JWT, a valid browser login state for the target zone, and the presence of a self-referential OIDC provider configuration — this is not a pre-authentication vulnerability, and does not by itself grant privileges beyond those already held by the mapped shadow account.

Source published

6 Oct 2026 07:06:18 UTC

Source modified

6 Oct 2026 11:49:21 UTC

Observed here

23 Oct 2026 15:48:27 UTC

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CVSS 4.0 · 6.5 CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:A/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N/E:P