Unauthenticated S3 object writes via presigned URLs
Published Jun 26, 2026 · Updated Jun 26, 2026
Missing authentication in Budibase before 3.39.3 allows remote attackers to mint S3 upload URLs using stored datasource credentials. The public POST /api/attachments/:datasourceId/url route applies only reCAPTCHA, loads enriched S3 secrets, and signs attacker-supplied bucket and key values. Exploitation requires a workspace ID, an S3 datasource ID, and PutObject permission, enabling object creation or overwrite within the credential's reach.
Summary
What happened
Missing authentication in Budibase before 3.39.3 allows remote attackers to mint S3 upload URLs using stored datasource credentials. The public POST /api/attachments/:datasourceId/url route applies only reCAPTCHA, loads enriched S3 secrets, and signs attacker-supplied bucket and key values. Exploitation requires a workspace ID, an S3 datasource ID, and PutObject permission, enabling object creation or overwrite within the credential's reach.
The record
- CVE
- CVE-2026-50136
- Published
- Jun 26, 2026
- Updated
- Jun 26, 2026
- Vendor
- Budibase
- Product
- Budibase
- Classifications
- CWE-306, T1190
- Attack vector
- network
- Privileges
- unauthenticated
Timeline
How it unfolded
- Jun 26, 2026CVE publishedPublication date reported by the CVE source.
- Jun 26, 2026Record updatedLatest update available in the CVE record.
Exploitability
Present is not the same as exploitable
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Is a vulnerable build present?
Compare these published version ranges with your installed build and any vendor patches.
- Affected versionversion=< 3.39.3
What conditions does exploitation require?
What is affected?
Published CVSS scores
CVSS describes severity. EPSS estimates exploitation probability.
Attacks
What attackers are doing with it
Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.
Weakness, pattern, technique
Public exploit references
- Vendor non-destructive signed-upload validation procedureproof of concept · demonstrated
Labels summarize the accepted research assessment. They do not indicate a test against your environment.
Technologies
Your stack
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Your stack
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