# CVE-2026-50137: Budibase missing authorization in S3 pre-signed URL generation

Source: https://junglewise.ai/threats/cve-2026-50137-budibase-missing-authorization-in-s3-pre-signed-url-generation  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-06-26. Updated: 2026-09-25  
License: CC BY 4.0 with a link back

CVE-2026-50137 · Severity: high · CVSS 3.1 · Published 2026-06-26

Budibase is a low-code platform that allows organizations to build and deploy business applications. A critical flaw in its file-attachment endpoint allows unauthenticated attackers to generate temporary URLs that grant S3 write access using the application's stored AWS credentials. An attacker can upload files to any AWS S3 bucket the application has access to, potentially compromising sensitive data, injecting malware, or disrupting operations.

Technologies: [@budibase/server (npm)](https://junglewise.ai/threats/technologies/budibase-server). Vendors: [npm](https://junglewise.ai/threats/vendors/npm).

## Quick answers

**Is CVE-2026-50137 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-50137 being exploited in the wild.

**How severe is CVE-2026-50137?** High severity, with a CVSS score of 3.1, published 26 June 2026.

**Which products and versions are affected?** @budibase/server (npm) < 3.39.0, SEMVER:introduced=0,fixed=3.39.0.

**Is there a fix for CVE-2026-50137?** Yes. @budibase/server (npm): upgrade to 3.39.0 or later. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**How is CVE-2026-50137 attacked?** It is attacked over the network, in a web application.

**Am I affected by CVE-2026-50137?** Check whether you run @budibase/server (npm) at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## How to fix

- @budibase/server (npm): upgrade to 3.39.0 or later

  ```sh
  npm install @budibase/server@3.39.0
  ```


## Technical details

The vulnerability is an authentication bypass in the POST /api/attachments/:datasourceId/url endpoint (packages/server/src/api/routes/static.ts). Unlike all other mutating endpoints on the same router, this endpoint lacks the authorized(...) middleware, instead relying only on recaptcha middleware which is disabled by default and skipped for non-production workspaces. The controller (getSignedUploadURL) accepts an attacker-supplied bucket and key parameter, then uses sdk.datasources.get() to retrieve S3 credentials for the specified datasource and instantiates an AWS S3 client with those credentials. It returns an AWS Signature V4 pre-signed PutObjectCommand URL valid for 15 minutes. The workspace context is derived from the x-budibase-app-id header, body appId, path segment, or query parameter, and auth.buildAuthMiddleware runs with publicAllowed: true. The currentWorkspace dev-preview check bypasses non-browser clients (such as curl or custom tools), allowing access to development workspaces. An attacker must know or enumerate a workspace ID (app_...) and datasource ID (ds_...), both trivially enumerable in many deployments. The fix is available in version 3.39.0 and later.

## Affected products

- Budibase @budibase/server <3.39.0

## Identifiers

- CVE-2026-50137
- GHSA-35c4-rvc8-frhm

## Timeline

- 2026-05-28: disclosed
- 2026-05-28: patched: Patched in version 3.39.0

## References

- [https://github.com/Budibase/budibase/security/advisories/GHSA-35c4-rvc8-frhm](https://github.com/Budibase/budibase/security/advisories/GHSA-35c4-rvc8-frhm)
- [https://github.com/Budibase/budibase](https://github.com/Budibase/budibase)

## Related threats

- [Budibase S3 signed upload URL issuance via attachments endpoint](https://junglewise.ai/threats/cve-2026-54356-budibase-s3-signed-upload-url-issuance-via-attachments-endpoint)
- [Budibase automation SSRF in webhook and integration steps](https://junglewise.ai/threats/cve-2026-35219-budibase-automation-ssrf-in-webhook-and-integration-steps)
- [Budibase S3 presigned URL authorization regression](https://junglewise.ai/threats/cve-2026-72859-budibase-s3-presigned-url-authorization-regression)
- [Budibase MySQL DESCRIBE backtick injection via multipleStatements](https://junglewise.ai/threats/cve-2026-73408-budibase-mysql-describe-backtick-injection-via-multiplestatements)
- [Budibase privilege escalation in public role assignment API](https://junglewise.ai/threats/cve-2026-73305-budibase-privilege-escalation-in-public-role-assignment-api)