CVE-2026-72859 in Budibase
Summary
by MITRE • 08/14/2026
Budibase versions 3.39.4 before 3.40.0 contain an authorization regression in the S3 attachment upload endpoint that allows BASIC users to obtain S3 PutObject presigned URLs by sending POST requests to the attachments endpoint. The route was changed from a BUILDER permission check to a TABLE/WRITE check, which BASIC users hold by default. Attackers can specify arbitrary S3 buckets in the request body to generate presigned URLs for writing to any bucket accessible by the stored IAM credentials, enabling unauthorized file uploads.
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Analysis
by VulDB Data Team • 08/14/2026
This vulnerability represents a critical authorization regression in Budibase's S3 attachment handling functionality that fundamentally undermines the application's access control model. The flaw manifests in the transition of permission validation from a BUILDER level check to a TABLE/WRITE permission requirement, creating an unintended privilege escalation vector. When BASIC users submit POST requests to the attachments endpoint, they can leverage this misconfiguration to obtain presigned URLs for S3 PutObject operations without proper authorization. The vulnerability stems from an improper security boundary that was introduced during a code refactoring or feature update process, where the permission validation logic was weakened to accommodate broader access patterns.
The technical implementation of this flaw allows attackers to manipulate request parameters by specifying arbitrary S3 bucket names within the request body, effectively bypassing the intended authorization controls. This regression enables unauthorized file uploads through the generation of presigned URLs that utilize stored IAM credentials with elevated permissions. The underlying mechanism relies on the application's inability to properly validate user roles against the specific resource access being requested. From a cybersecurity perspective, this vulnerability directly violates the principle of least privilege and creates an attack surface where unauthenticated or low-privileged users can gain write access to arbitrary S3 storage locations. The issue manifests as a path traversal-like behavior in the authorization system, where the permission model fails to properly restrict access based on user roles.
The operational impact of this vulnerability extends beyond simple unauthorized file uploads, creating potential for data exfiltration, malicious payload deployment, and persistence mechanisms within cloud storage environments. Attackers can leverage this flaw to upload malware or phishing materials to any S3 bucket accessible by the application's IAM credentials, potentially compromising multiple cloud resources and storage accounts. The vulnerability affects organizations that rely on Budibase for document management and file attachment handling, particularly those with multi-tenant architectures where different users or teams share common S3 storage resources. This regression creates a significant risk of data loss or corruption when attackers can write to sensitive storage locations, as well as potential compliance violations in regulated environments.
Mitigation strategies should focus on immediate patching of the affected versions and implementation of proper permission validation controls. Organizations must ensure that access to S3 presigned URL generation endpoints is restricted to appropriate user roles with explicit BUILDER permissions rather than default TABLE/WRITE access. Security configurations should enforce strict validation of bucket names against authorized storage locations and implement additional checks to prevent arbitrary bucket specification in upload requests. The fix should align with security best practices outlined in the CWE 284 Access Control Checks and ATT&CK techniques related to privilege escalation and persistence through cloud services. Regular security testing and automated vulnerability scanning should be implemented to detect similar authorization regressions in other application endpoints, particularly those involving external service integrations and cloud storage access controls.