Can you explain this vulnerability to me?

CVE-2026-48153 is a Server-Side Request Forgery (SSRF) vulnerability in Budibase versions prior to 3.39.0. It occurs because the fetchToken function in the OAuth2 SDK makes a POST request to a user-supplied URL without enforcing blacklist checks that are used elsewhere in the codebase.

The Joi schema for the OAuth2 URL does not restrict the scheme or host, allowing attackers to send requests to internal hosts or cloud metadata endpoints. This means an attacker can exploit this to make the server send requests to internal services that should normally be inaccessible.

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How can this vulnerability impact me? :

This vulnerability can have serious impacts including cross-tenant data exfiltration and credential theft.

• Attackers can bypass tenant isolation and enumerate other tenants' databases such as CouchDB databases, user data, and app definitions.
• Attackers can exfiltrate IAM credentials by targeting AWS cloud metadata endpoints, exposing instance role credentials and associated permissions.
• Self-hosted deployments are vulnerable to access to local services like CouchDB, Redis, MinIO, or other hosts in the pod network.

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How can this vulnerability be detected on my network or system? Can you suggest some commands?

This vulnerability can be detected by monitoring for unusual POST requests made by the Budibase OAuth2 SDK to builder-supplied URLs that bypass blacklist checks. Specifically, look for outbound requests targeting internal IP ranges such as 127.0.0.1, 169.254.169.254, or other private IP addresses that should normally be blocked.

Network detection can involve capturing and analyzing HTTP POST requests from Budibase instances to internal or cloud metadata endpoints, especially those that should be inaccessible.

Suggested commands to detect potential exploitation include using network monitoring tools like tcpdump or curl to test access to internal endpoints from the Budibase server.

• Use tcpdump to capture outbound POST requests from the Budibase server: tcpdump -i <interface> 'tcp and dst net 127.0.0.0/8 or dst net 169.254.0.0/16'
• Use curl from the Budibase server to test access to internal metadata endpoints: curl -X POST http://169.254.169.254/latest/meta-data/iam/security-credentials/
• Check application logs for OAuth2 token fetch attempts to unexpected or internal URLs.

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What immediate steps should I take to mitigate this vulnerability?

The immediate mitigation step is to upgrade Budibase to version 3.39.0 or later, where the vulnerability is fixed.

If upgrading is not immediately possible, apply the recommended fix by adding blacklist validation before the fetch call in the OAuth2 SDK and setting the fetch configuration to use redirect mode "manual" instead of "follow".

Alternatively, replace the vulnerable fetch call with the secure fetchWithBlacklist function that enforces blacklist checks and redirect validation.

Additionally, restrict network access to internal IP ranges and cloud metadata endpoints from the Budibase server to reduce the attack surface.

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How does this vulnerability affect compliance with common standards and regulations (like GDPR, HIPAA)?:

CVE-2026-48153 enables cross-tenant data exfiltration by bypassing tenant isolation, allowing attackers to enumerate other tenants' databases and potentially access sensitive information. It also permits exfiltration of IAM credentials from AWS cloud metadata endpoints, exposing instance role credentials with associated permissions.

Such unauthorized access and data leakage can lead to violations of data protection regulations and standards like GDPR and HIPAA, which require strict controls on data confidentiality and access. The high confidentiality impact of this SSRF vulnerability increases the risk of non-compliance with these regulations.

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