CVE-2026-50136: Budibase: Unauthenticated S3 signed upload URL generation allows arbitrary writes with stored datasource credentials

Severity: medium (CVSS 5.3 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.3% probability of exploitation in the next 30 days
Public exploit or detection template: yes
Published: 2026-06-26 · updated 2026-06-30
Weakness: CWE-306

Description

Budibase is an open-source low-code platform. Prior to 3.39.3, the application server exposes an unauthenticated endpoint that generates S3 PutObject presigned URLs using credentials stored in a workspace datasource. The route is protected only by the recaptcha middleware and does not require authentication, table permission, datasource permission, or builder access. A public caller who knows a workspace ID and S3 datasource ID can request a signed upload URL for attacker-controlled bucket and key values. This vulnerability is fixed in 3.39.3.

Affected products

budibase: before 3.39.3 — fixed in 3.39.3

How to fix

Upgrade to a fixed version: budibase 3.39.3. Check the vendor advisory for mitigations.

References

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