{"cve":"CVE-2026-50137","nvd":{"published":"2026-06-26T21:16:34.673","modified":"2026-06-30T19:49:18.990","status":"Analyzed","description":"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.","cvss_v4":{"vector":"CVSS:4.0/AV:N/AC:H/AT:N/PR:N/UI:N/VC:N/VI:H/VA:N/SC:N/SI:N/SA:N","score":8.2},"cvss_v3":{"version":"3.1","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:L","score":9.4},"cwes":["CWE-862"],"references":["https://github.com/Budibase/budibase/security/advisories/GHSA-35c4-rvc8-frhm","https://github.com/Budibase/budibase/security/advisories/GHSA-35c4-rvc8-frhm"],"products":["budibase:budibase"],"source":"nvd","synced_at":"2026-10-19T22:41:17.107060303+00:00"},"epss":{"cve":"CVE-2026-50137","score":0.00415,"percentile":0.35812,"date":"2026-10-31"},"kev":null,"osv":[{"id":"GHSA-35c4-rvc8-frhm","url":"https://osv.dev/vulnerability/GHSA-35c4-rvc8-frhm","summary":"Budibase: POST /api/attachments/:datasourceId/url is unauthenticated and lets anonymous callers mint S3 PUT pre-signed URLs using stored datasource IAM credentials","modified":"2026-07-21T15:15:49.070952439Z","packages":[{"ecosystem":"npm","name":"@budibase/server","purl":"pkg:npm/%40budibase/server","ranges":["<3.39.0"],"fixed":["3.39.0"]}]}],"attribution":["This product uses the NVD API but is not endorsed or certified by the NVD.","EPSS scores: FIRST Exploit Prediction Scoring System, https://www.first.org/epss","Known exploited vulnerabilities: CISA Known Exploited Vulnerabilities Catalog, https://www.cisa.gov/known-exploited-vulnerabilities-catalog","Package advisories: OSV (https://osv.dev), from the GitHub Advisory Database, PyPA, Go, RustSec and other ecosystem databases, under CC-BY 4.0 or CC0","CVE records: the CVE Program's CVE List (https://www.cve.org), under its terms of use (https://www.cve.org/Legal/TermsOfUse). CVE is a registered trademark of The MITRE Corporation; this product is not affiliated with the CVE Program."]}