CVE-2023-20903 : Security Advisory and Response

This CVE disclosure addresses a vulnerability related to UAA refresh tokens and external identity providers. The issue arises when an external identity provider is linked to the UAA (User Account and Authentication service). If a refresh token is issued to a client on behalf of a user from that identity provider and the administrator deactivates the identity provider from the UAA, the UAA fails to reject the refresh token during a refresh token grant. This oversight allows the UAA to continue issuing access tokens to requests presenting such refresh tokens, providing unauthorized access to Cloud Foundry resources.

Understanding CVE-2023-20903

This section delves deeper into the nature of CVE-2023-20903 and its implications.

What is CVE-2023-20903?

CVE-2023-20903 revolves around the failure of the UAA to revoke refresh tokens associated with deactivated external identity providers, enabling continued access to Cloud Foundry resources.

The Impact of CVE-2023-20903

The vulnerability poses a significant security risk as it allows clients with refresh tokens issued through the deactivated identity provider to maintain access to Cloud Foundry resources until the refresh token expires, which is typically after 30 days.

Technical Details of CVE-2023-20903

This section provides more technical insights into the vulnerability.

Vulnerability Description

The vulnerability in CVE-2023-20903 lies in the failure of the UAA to properly handle refresh tokens when linked external identity providers are deactivated, leading to unauthorized access to Cloud Foundry resources.

Affected Systems and Versions

The vulnerability affects all versions of Cloud Foundry where external identity providers are linked to the UAA.

Exploitation Mechanism

Exploiting CVE-2023-20903 involves obtaining a refresh token from a deactivated external identity provider and using it to maintain access to Cloud Foundry resources beyond the intended deactivation period.

Mitigation and Prevention

To address the CVE-2023-20903 vulnerability, immediate steps should be taken along with the implementation of long-term security practices.

Immediate Steps to Take

Administrators should monitor and revoke refresh tokens associated with deactivated external identity providers to prevent unauthorized access.
Consider implementing additional authentication measures for enhanced security.

Long-Term Security Practices

Regularly review and update access control policies to mitigate similar vulnerabilities in the future.
Conduct security training for personnel to raise awareness about proper access management protocols.

Patching and Updates

Cloud Foundry users are advised to update to the latest version that includes a patch for CVE-2023-20903 to ensure the vulnerability is addressed and secure access control measures are in place.