CVE-2026-47840: UAA LDAP Certificate Validation Bypass – Credential Harvesting & Privilege Escalation

Technical summary

CVE-2026-47840 is a certificate validation and credential harvesting vulnerability in UAA's LDAP authentication implementation over StartTLS. The vulnerability stems from insufficient certificate validation during the StartTLS handshake with the LDAP directory server. An attacker on the network path can present any valid certificate from any trusted Certificate Authority—not necessarily one bound to the LDAP server's identity—to establish a TLS session. Once the encrypted channel is established under the attacker's control, the attacker can harvest the plaintext bind credentials used by UAA to authenticate to LDAP, as well as all end-user passwords transmitted via simple-bind authentication. Additionally, the attacker can inject forged LDAP responses that populate group memberships and authorization attributes, allowing the attacker to grant themselves administrative scopes within the UAA system. The vulnerability affects UAA versions prior to v78.13.0 and cf-deployment versions prior to v56.2.0.

Business impact

This vulnerability enables account takeover, privilege escalation, and data exfiltration in Cloud Foundry and UAA deployments. An attacker can harvest credentials for both service accounts (LDAP bind credentials) and end users, then use elevated group memberships to gain administrative access to the entire authentication system. The consequence is unauthorized access to all systems and data protected by UAA, potential lateral movement across cloud infrastructure, and loss of audit trail integrity if the attacker modifies authentication records. For organizations using LDAP-backed UAA as their identity provider, this represents a critical control plane compromise.

Affected systems

The vulnerability affects all deployments using UAA versions prior to v78.13.0 and cf-deployment versions prior to v56.2.0 that authenticate users against LDAP over StartTLS. Organizations running older versions of Cloud Foundry or standalone UAA instances with LDAP integration are at risk. The attack requires the attacker to be on the network path between the UAA instance and the LDAP directory server, such as a compromised network segment, misconfigured network routing, or a rogue network device. Cloud-hosted and on-premises deployments are both vulnerable if network isolation controls are absent.

Exploitability

The attack requires network positioning (man-in-the-middle capability) between UAA and LDAP, which carries a complexity rating of High. However, once that position is achieved, the exploitation is straightforward and requires no user interaction, no authentication, and no special knowledge of the target environment. The attacker leverages standard LDAP protocol behavior and certificate validation weaknesses rather than complex logic flaws. Organizations without proper network segmentation between authentication layers face elevated exploitability. The vulnerability is not currently listed on the CISA KEV catalog, indicating no widespread active exploitation has been publicly documented at the time of disclosure.

Remediation

Upgrade UAA to version v78.13.0 or later, and cf-deployment to version v56.2.0 or later. These versions implement proper certificate validation that verifies the LDAP server certificate is bound to the expected LDAP server identity, preventing certificate substitution attacks. Organizations should verify compatibility with their current Cloud Foundry and application versions before deploying patches. Until patching is complete, network isolation and segmentation should be enforced to prevent unauthenticated network access to the LDAP authentication path.

Patch guidance

Apply UAA v78.13.0 or newer and cf-deployment v56.2.0 or newer. Verify patch installation by confirming the deployed version numbers match or exceed the fixed versions. Test the patched environment in a non-production setting to ensure LDAP authentication continues to function correctly and that group membership resolution works as expected. Monitor authentication logs after patching for any anomalies. If you are running a custom UAA deployment not managed by cf-deployment, consult the UAA release notes to identify the exact patch version and apply it to your infrastructure.

Detection guidance

Monitor network traffic between UAA and LDAP for unexpected certificate chains or certificate rotation patterns. Implement certificate pinning or certificate transparency logging to detect unauthorized certificates presented during StartTLS negotiation. Review UAA authentication logs for anomalous group membership assignments, especially those granting admin or elevated scopes to previously unprivileged accounts. Monitor LDAP bind events for unexpected or suspicious credential usage. Detect man-in-the-middle positioning through network segmentation monitoring, ARP spoofing detection, and BGP hijacking alerts. Correlate authentication anomalies with network telemetry to identify potential simultaneous network and authentication attacks.

Why prioritize this

This vulnerability merits immediate priority despite the High (not Critical) CVSS score because it enables complete compromise of the authentication control plane. The combination of credential harvesting, privilege escalation via forged group memberships, and authentication system impersonation creates a compound risk. The requirement for network positioning reduces exploitability in well-segmented networks, but the impact—if achieved—is near-total. Organizations should prioritize patching within their standard critical vulnerability timeline (days, not weeks), with network isolation as a temporary mitigation if patching is delayed.

Risk score, explained

The CVSS 3.1 score of 7.5 (HIGH) reflects a network-based attack with High complexity (due to man-in-the-middle positioning requirement), no required privileges, no user interaction, changed scope (impacts confidentiality of the system and services it protects), low confidentiality impact, and high integrity impact. The score appropriately captures the authentication system compromise and privilege escalation path, but does not fully reflect the organizational risk of losing control of identity and access management, which justifies prioritization above the numeric score alone.

Frequently asked questions