Budibase: Unauthenticated S3 signed upload URL generation allows arbitrary writes with stored datasource credentials

published 2026-06-22 4 mo ago modified 2026-07-17 3 mo ago also EUVD-2026-39912 , GHSA-jj36-r9w3-3pfh

cvss: 7.4; version 3.1, CNA
cisa kev: Not listed; not in CISA's catalog
epss: 0.3%; EPSS 0.3% chance of exploitation in 30 days, percentile 21%
public exploits: 0; none known

Budibase is an open-source low-code platform. Prior to 3.39.3, the application server exposes an unauthenticated endpoint that generates S3 PutObject presigned URLs using credentials stored in a workspace datasource. The route is protected only by the recaptcha middleware and does not require authentication, table permission, datasource permission, or builder access. A public caller who knows a workspace ID and S3 datasource ID can request a signed upload URL for attacker-controlled bucket and key values. This vulnerability is fixed in 3.39.3.

Patch / fix

fixed in 2 links 2

npm @budibase/server 3.39.2
budibase budibase 3.39.3

github.com/Budibase/budibase@d9dbb7f commit
github.com/Budibase/budibase#18774 pull request

CISA SSVC

Exploitation: Proof of concept is public
Automatable: no
Technical impact: partial
Assessed: 4 mo ago (2026-06-27)

Exploit prediction

0.29% chance of exploitation in the next 30 days, higher than 21% of all scored CVEs (FIRST EPSS, 2026-11-08).

Exploits and checks

github.com https://github.com/Budibase/budibase/security/advisories/GHSA-jj36-r9w3-3pfh referenced PoC, tagged "exploit" by a source, unverified

CVSS scores

assigned by	version	score	vector
CNA	3.1	7.4	CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:L/I:L/A:L
GitHub	3.1	7.4	CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:L/I:L/A:L
NVD	3.1	5.3	CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N

Affected packages

ecosystem	package	affected	fixed in
npm	@budibase/server	<3.39.2	3.39.2

Affected products

Budibase budibase

Classification

Weakness

CWE-306 Missing Authentication for Critical Functionality

References

github.com /Budibase/budibase/pull/18774
web
github.com /Budibase/budibase/commit/d9dbb7f6105373cc88ecacdbcab70c776f7dd6a1
web
github.com /Budibase/budibase/security/advisories/GHSA-jj36-r9w3-3pfh
exploit, web, vendor-advisory
nvd.nist.gov /vuln/detail/CVE-2026-50136
advisory
github.com /Budibase/budibase
package

Sources

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.

CPEs and fixed versions use Anchore's correction of NVD's data: Added CPE configurations because not yet analyzed by NVD.

Summary