GHSA-35c4-rvc8-frhm · Severity: high · Ecosystem: npm — Budibase: POST /api/attachments/:datasourceId/url is unauthenticated and lets anonymous callers mint S3 PUT pre-signed URLs using stored datasource IAM credentials
Budibase is an open-source low-code platform. Prior to 3.39.0, an anonymous attacker who knows or can enumerate a workspace id (app_...) and an S3-source datasource id (ds_...) can call this endpoint with no auth and obtain a 15-minute pre-signed PUT URL minted on the victim's IAM identity. The endpoint also returns the publicUrl so the attacker knows exactly where their PUT lands. Because bucket is attacker-controlled, the attacker can write to any bucket those IAM credentials can write to, not only the bucket the datasource was configured for. The Budibase server route POST /api/attachments/:datasourceId/url (packages/server/src/api/routes/static.ts) is registered with only the recaptcha middleware. There is no authorized(...) middleware in the chain. The controller (packages/server/src/api/controllers/static/index.ts::getSignedUploadURL) looks the requested datasource up, instantiates an AWS S3 client with the datasource's stored accessKeyId / secretAccessKey, and returns an AWS Signature V4 pre-signed PutObjectCommand URL for the caller-supplied bucket and key. The bucket is not pinned to the datasource's configured bucket. The workspace context required by sdk.datasources.get is sourced by getWorkspaceIdFromCtx (packages/backend-core/src/utils/utils.ts) from any of: the x-budibase-app-id header, the JSON body appId, a path segment that begins with the workspace prefix, or ?appId=. auth.buildAuthMiddleware([], { publicAllowed: true }) runs before any of this and explicitly allows anonymous requests. The currentWorkspace middleware's "deny access to dev preview" branch only triggers under isBrowser(ctx) && !isApiKey(ctx); isBrowser checks the parsed User-Agent for a recognised browser, so any non-browser client (curl, the supplied PoC, any tool not setting a browser UA) is neither and reaches dev workspaces too. This vulnerability is fixed in 3.39.0.
Conclusion & alert: CVE-2026-50137 is rated Exploit Available (59.5/100): CVSS High severity, with low exploitation likelihood (EPSS 0.41%). Core evidence: 1 public exploit reference(s) are indexed (Exploit-DB). Mandatory action: Public exploits are available—assess exposure, apply mitigations, and prioritize patching.
Risk is dynamic; we continuously reassess and refresh what is shown on this page as upstream context changes.
| EDB-ID | Source | Kind | Published | Link |
|---|---|---|---|---|
| — | nvd_ref | exploit_tag | Exploit-DB ↗ |
EPSS lead: Daily EPSS estimates relative likelihood of exploitation; percentile ranks this CVE among scored vulnerabilities (higher = more severe relative rank).
| # | Date | Old EPSS score | New EPSS score | Delta (New - Old) |
|---|---|---|---|---|
| 1 | 2026-07-01 | 0.34% | 0.41% | +0.07% |
| 2 | 2026-06-27 | 0.02% | 0.34% | +0.32% |
| 3 | 2026-06-12 | — | 0.02% | — |
Full EPSS history (3 records total)
CVSS metrics for this CVE.
| Base score | Version | Severity | Vector | Exploitability | Impact | Score source |
|---|---|---|---|---|---|---|
| 8.2 | 4.0 | HIGH |
|
— | — | [email protected] |
| 9.4 | 3.1 | CRITICAL |
|
3.9 | 5.5 | [email protected] |
GHSA-35c4-rvc8-frhm · Severity: high · Ecosystem: npm — Budibase: POST /api/attachments/:datasourceId/url is unauthenticated and lets anonymous callers mint S3 PUT pre-signed URLs using stored datasource IAM credentials
| URL | Tags |
|---|---|
| https://github.com/Budibase/budibase/security/advisories/GHSA-35c4-rvc8-frhm | Exploit Mitigation Vendor Advisory |