EUVD-2026-36311
GHSA-wx8w-j86h-c458
Severity by source
AV:N/AC:H/PR:N/UI:N/S:C/C:H/I:H/A:H
Network-reachable SAML endpoint with no auth or user interaction; AC:H because exploitation requires non-default wantAssertionSigned=false config; S:C reflects platform-wide impersonation; A:N - described impact is identity spoofing, not availability.
Primary rating from Vendor (vmware).
CVSS VectorVendor: vmware
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:H/I:H/A:H
Lifecycle Timeline
2DescriptionCVE.org
Cloud Foundry UAA incorrectly treated XML encryption to the Service Provider (confidentiality) as a substitute for XML signatures from the Identity Provider (authenticity) in two SAML flows: the OAuth 2.0 SAML2 bearer grant (token endpoint) and browser SSO (ACS) when wantAssertionSigned is set to false. Assertions or responses that were unsigned but contained encrypted content could still be accepted. Encryption uses the SP's public key from published metadata, therefore, any party, not only a trusted IdP, can produce ciphertext UAA can decrypt; successful decryption therefore does not prove the IdP issued the message.
Affected versions: Cloud Foundry UAA (uaa_release) 2.0.0 through 78.13.0. Cloud Foundry CF Deployment all versions through 56.1.0.
AnalysisAI
Authentication bypass in Cloud Foundry UAA (User Account and Authentication) versions 2.0.0 through 78.13.0 allows remote attackers to forge SAML assertions and impersonate users by exploiting a logic flaw where XML encryption was accepted as a substitute for XML signature verification. Because the Service Provider's public encryption key is published in SAML metadata, any party - not just a trusted Identity Provider - can craft encrypted-but-unsigned assertions that UAA will decrypt and trust, breaking the identity-assurance guarantee of SAML. …
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Attack ChainAIDerived
Hypothetical attack flow derived from CVE metadata
Vulnerability AssessmentAI
| Exploitation | Target UAA must have at least one SAML IdP provider configuration with wantAssertionSigned set to false (the vulnerable code path explicitly checks this flag), and either the OAuth 2.0 SAML2 bearer grant must be enabled at the token endpoint or the browser SSO ACS endpoint must be reachable by the attacker. … Additional conditions and limiting factors are described in the full assessment. |
| Risk Assessment | The CVSS:3.1 vector AV:N/AC:H/PR:N/UI:N/S:C/C:H/I:H/A:H yields 9.0 (Critical) and is broadly consistent with the description: network-reachable SAML endpoints (AV:N), no authentication or user interaction required (PR:N/UI:N), and a scope change (S:C) reflecting that compromising UAA breaks the trust boundary into every downstream CF-managed resource. … Full risk analysis with EPSS, KEV, and SSVC signal comparison available after sign-in. |
| Exploit Scenario | An attacker fetches the target UAA's public SAML SP metadata (typically exposed at /saml/metadata) to obtain the SP encryption certificate, then crafts a SAML Response or Assertion that names a privileged victim user (e.g., a Cloud Foundry admin) in the Subject, encrypts the assertion to the SP's public key, and omits any IdP signature. The attacker POSTs this to the UAA ACS endpoint or exchanges it at the token endpoint via the SAML2 bearer grant, and UAA - finding wantAssertionSigned=false and successfully decrypting the payload - issues an OAuth access token as the impersonated user, granting full platform control. … |
| Remediation | Upgrade uaa_release beyond 78.13.0 and cf-deployment beyond 56.1.0 to the patched release line per the Cloud Foundry advisory at https://www.cloudfoundry.org/blog/cve-2026-41005-uaa-accepts-saml-encrypted-assertions-authentication-bypass/; the input data does not state an exact fixed version, so consult the advisory for the current minimum safe release. … Detailed patch versions, workarounds, and compensating controls in full report. |
Recommended ActionAI
Within 24 hours: Identify and inventory all Cloud Foundry UAA instances running versions 2.0.0-78.13.0; implement immediate network segmentation to restrict SAML assertion traffic to known, trusted Identity Providers only. …
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