Budibase authenticated arbitrary S3 signed upload URL issuance via /api/attachments/:datasourceId/url

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS

7.1 · CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:H/A:L

EPSS

• CVE-2026-54356: 0.35% estimated exploitation activity in the next 30 days; percentile 28.87 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.

As published by the source; long descriptions are shortened.

Summary Budibase 3.39.7 allows a low-privilege authenticated published-app user with the built-in BASIC role to obtain arbitrary S3 pre-signed upload URLs backed by a workspace datasource's stored server-side credentials. The affected endpoint is: POST /api/attachments/:datasourceId/url The caller can control: and receives: This lets a low-privilege published-app user mint S3 PUT URLs using server-side datasource credentials for attacker-chosen object destinations. Steps: 1. Log in as an admin user. 2. Create a new app/workspace. 3. In the development app context, create an S3 datasource with valid credentials. 4. Publish the app. 5. Create a low-privilege user with the built-in BASIC role on the published production app ID. 6. Log in as that BASIC user. 7. Send: POST /api/attachments/<datasourceId/url with: and the published app header: Observe a successful response containing: Observed result The following behavior: dev BASIC request: 403 User does not have permission app publish:…

Published by the source

26 Aug 2026, 14:07 UTC

Last modified by the source

26 Aug 2026, 14:07 UTC

Source last checked

26 Oct 2026, 13:01 UTC

1. Revision 1 · created · 26 Oct 2026

   Published from ghsa record GHSA-6x9p-4r67-5gjx

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# Patch Next advisory brief: CVE-2026-54356

Advisory: Budibase authenticated arbitrary S3 signed upload URL issuance via `/api/attachments/:datasourceId/url`
IDs: CVE-2026-54356, GHSA-6x9p-4r67-5gjx
Record: https://patchnext.com/advisories/cve-2026-54356 (revision 1, source checked 26 Oct 2026, 13:01 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: High (CVSS 7.1)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor response not established. A vendor fix does not mean a deployment is fixed.

## Affected components
- npm @budibase/server: affected <= 3.38.1

## Suggested inspection (read-only)
- `npm ls @budibase/server --all`: lists every installed copy and version, including transitive ones. Run in the project root after `npm ci`.

## Supported action
No complete vendor fix is recorded. Follow the primary source's mitigation guidance and check this record again before closing anything.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on @budibase/server.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://github.com/advisories/GHSA-6x9p-4r67-5gjx (GitHub-reviewed advisory GHSA-6x9p-4r67-5gjx lists affected ranges: npm @budibase/server >=0 <=3.38.1)

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