# CVE-2026-50137: Budibase: POST /api/attachments/:datasourceId/url is unauthenticated and lets anonymous callers mint S3 PUT pre-signed URLs using stored datasource IAM credentials > Unauthenticated attackers can mint S3 pre-signed URLs using stored IAM credentials, allowing unauthorized writes to arbitrary buckets. - **Severity:** High 8.2 (`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`) - **Exploited in the wild:** Not known - **Login needed:** Not needed - **Attackable:** Over the internet - **Victim action needed:** Not needed - **Fix available:** Yes - **Published:** 26 Jun 2026 - **Updated:** 29 Jun 2026 - **Also known as:** GHSA-35c4-rvc8-frhm ## What is CVE-2026-50137? CVE-2026-50137 is a high-severity missing authorization vulnerability in budibase, published on 26 Jun 2026. An attacker can exploit it over the internet without logging in, with no action from the victim. ### Official 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. Weakness: CWE-862 (Missing Authorization) ## Which versions are affected by CVE-2026-50137? 2 open source packages ship an affected version, including @budibase/server. It affects 1 product. | Package | Ecosystem | Affected | Fixed in | | --- | --- | --- | --- | | `@budibase/server` | npm | All versions | 3.39.0 | | `@budibase/server` | npm | All versions | 3.39.0 | Products: Budibase Budibase. ## How do I fix CVE-2026-50137? Upgrade @budibase/server to 3.39.0 or later. ## Is CVE-2026-50137 being exploited? It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-50137 exists. ## Other vulnerabilities in budibase - [CVE-2026-54350](https://insights.sbomify.com/CVE-2026-54350/): Budibase: Anonymous NoSQL operator injection via published-app query templates (critical 10.0) - [CVE-2026-27702](https://insights.sbomify.com/CVE-2026-27702/): Budibase Vulnerable to Remote Code Execution via Unsafe eval() in View Filter Map Function (Budibase Cloud) (critical 9.9) - [CVE-2026-54352](https://insights.sbomify.com/CVE-2026-54352/): Budibase: Arbitrary file read by workspace-builder via PWA-zip symlink upload (critical 9.6) - [CVE-2026-31818](https://insights.sbomify.com/CVE-2026-31818/): Budibase: Server-Side Request Forgery via REST Connector with Empty Default Blacklist (critical 9.6) - [CVE-2026-30240](https://insights.sbomify.com/CVE-2026-30240/): Budibase PWA ZIP Upload Path Traversal Allows Reading Arbitrary Server Files Including All Environment Secrets (critical 9.6) ## Fix prompt for AI coding agents ```text Check this codebase for CVE-2026-50137 and fix it if it is affected. What it is: CVE-2026-50137 is a high-severity missing authorization vulnerability in budibase, published on 26 Jun 2026. An attacker can exploit it over the internet without logging in, with no action from the victim. Exploitation: It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-50137 exists. Affected packages and fixed versions: - @budibase/server (npm): affected all versions; fixed in 3.39.0 - @budibase/server (npm): affected all versions; fixed in 3.39.0 Task: 1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies. 2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it. 3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead. 4. Run the tests and summarise what changed and why. 5. If nothing in the project is affected, say so and change nothing. Reference: https://insights.sbomify.com/CVE-2026-50137/ (Markdown: https://insights.sbomify.com/CVE-2026-50137/index.md) ``` ## Sources - CVE record: https://www.cve.org/CVERecord?id=CVE-2026-50137 - NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-50137 - OSV: https://osv.dev/vulnerability/CVE-2026-50137 --- From sbomify Insights: https://insights.sbomify.com/CVE-2026-50137/ Summaries are generated and may contain mistakes; the official description above is the record.