CVE-2026-72859 — @budibase/server
CVE-2026-72859 is a CWE-863 vulnerability in @budibase/server. No vendor fix is recorded yet; mitigation options are listed below.
Budibase 3.39.4 before 3.40.0 Authorization Regression via S3 Presigned URL
Exploitation Status
Proof-of-concept exploit code exists
- CISA’s SSVC triage found public proof-of-concept exploit code for this CVE, though no confirmed active exploitation.
Exploitation and automatability from CISA’s SSVC triage for CVE-2026-72859.
EPSS Exploitation Probability
Probability of exploitation in the next 30 days, from FIRST.org EPSS.
Real-World Exposure
How broadly this vulnerability is actually deployed: weekly install volume shows current usage, and reverse-dependency count shows how many other packages break if it stays unpatched.
@budibase/servernpmDescription
Impact
In Budibase v3.39.4, a regression in the authorization level for the S3 attachment upload endpoint allows any BASIC app user to obtain S3 PutObject presigned URLs. The endpoint uses TABLE/WRITE permission level instead of the intended BUILDER level defined in v3.39.3. Additionally, the controller does not pin the target bucket to the datasource's configured bucket, allowing writes to any S3 bucket the stored IAM credentials can access.
Reproduction
- As a BASIC app user, discover or obtain a valid S3 datasource ID within the app
- Send a POST request:
POST /api/attachments/<datasourceId>/url
Content-Type: application/json
x-budibase-app-id: <appId>
{"bucket": "target-bucket", "key": "malicious-file.html"}
- The response contains a valid S3 PutObject presigned URL
- Use the presigned URL to upload arbitrary content to any writable S3 bucket in the IAM credential scope
Root Cause
The /api/attachments/:datasourceId/url route was changed from authorized(BUILDER) in v3.39.3 to authorized(PermissionType.TABLE, PermissionLevel.WRITE) in v3.39.4. BASIC users have TABLE/WRITE permissions by default, so they can call this endpoint. The controller at packages/server/src/api/controllers/static/index.ts:614-632 accepts the bucket parameter directly from the request body and passes it to getSignedUrl without validating against the datasource's configured bucket.
Evidence
The test suite at packages/server/src/api/routes/tests/static.spec.ts:218-235 confirms this behavior. The test authenticates as a BASIC role user and successfully generates a signed upload URL, verifying HTTP 200 and a defined res.body.signedUrl.
Remediation
- Restore the
authorized(BUILDER)middleware on the route - Add
paramResource("datasourceId")to ensure the datasource belongs to the caller's app - Pin the S3 bucket to
datasource.config.bucketin the controller, ignoring the caller-supplied bucket value
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 📦npm | @budibase/server | all versions | No fix |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for @budibase/server, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Remediation status
No patched version of @budibase/server has shipped for CVE-2026-72859 yet. Where your build allows, override or pin the dependency away from the vulnerable range, and apply any maintainer-recommended mitigation.
Mitigate without a patch
Put an independent control in front of the weakness: restrict the affected endpoint or interface to trusted networks, require an additional authentication factor or proxy-level check, and invalidate existing sessions and credentials in case the flaw has already been used.
Frequently Asked Questions
Is CVE-2026-72859 in your dependencies?
Find it across npm, including transitive dependencies.