# CVE-2026-116187: Rclone authorization bypass in serve s3 multipart uploads

Source: https://junglewise.ai/threats/cve-2026-116187-rclone-from-v1-68-0-before-v1-75-2-contains-an-authorization  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-10-25. Updated: 2026-10-25  
License: CC BY 4.0 with a link back

CVE-2026-116187 · Severity: medium · CVSS 5 · Published 2026-10-25

Rclone's S3 server feature with authentication proxy allows multiple tenants to securely access separate backends using different access keys. A flaw in multipart upload handling fails to verify that requests belong to the requesting tenant, allowing one tenant to inject data into, complete, or abort another tenant's in-flight uploads if they discover the upload ID, and to view upload metadata across tenants.

Technologies: [Rclone](https://junglewise.ai/threats/technologies/rclone). Vendors: [Rclone](https://junglewise.ai/threats/vendors/rclone).

## Quick answers

**Is CVE-2026-116187 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-116187 being exploited in the wild.

**How severe is CVE-2026-116187?** Medium severity, with a CVSS score of 5, published 25 October 2026.

**Which products and versions are affected?** Rclone v1.68.0 to v1.75.1.

**Is there a fix for CVE-2026-116187?** Yes: fixed in v1.75.2. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**How is CVE-2026-116187 attacked?** It is attacked over the network, in a software library.

**Am I affected by CVE-2026-116187?** Check whether you run Rclone at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## How to fix

- Fixed in v1.75.2

## Technical details

The vulnerability is an authorization bypass in multipart upload operations (UploadPart, CompleteMultipartUpload, AbortMultipartUpload) that are resolved by upload ID alone without re-checking the authenticated tenant context. While ordinary S3 object operations properly scope to the caller's VFS via per-request context, multipart operations use a process-global map with no tenant dimension. An authenticated attacker with knowledge of a victim's bucket, object name, and upload ID—obtainable via ListMultipartUploads if they own a same-named bucket—can manipulate in-flight uploads; the victim's object key is fixed by the initiator so this is not arbitrary cross-tenant write of at-rest content, but upload and custom object metadata are leaked.

## Affected products

- Rclone Rclone v1.68.0 to v1.75.1

## Timeline

- 2026-10-09: disclosed
- 2026-10-25: advisory

## References

- [https://github.com/rclone/rclone/security/advisories/GHSA-35g6-9fjv-rmx5](https://github.com/rclone/rclone/security/advisories/GHSA-35g6-9fjv-rmx5)
- [https://www.vulncheck.com/advisories/rclone-1.68.0-before-1.75.2-authorization-bypass-in-serve-s3-multipart-uploads](https://www.vulncheck.com/advisories/rclone-1.68.0-before-1.75.2-authorization-bypass-in-serve-s3-multipart-uploads)

## Related threats

- [Rclone B2 backend credential exposure on HTTP redirects](https://junglewise.ai/threats/cve-2026-116196-rclone-before-v1-75-2-contains-a-credential-exposure)
- [Rclone path traversal in translateLink function](https://junglewise.ai/threats/cve-2026-116195-rclone-before-1-75-2-contains-a-path-traversal-vulnerability-in)
- [Rclone cross-site request forgery in pCloud OAuth callback](https://junglewise.ai/threats/cve-2026-116194-rclone-from-1-52-0-before-1-75-2-contains-a-cross-site-request)
- [Rclone serve webdav authentication bypass via OPTIONS requests](https://junglewise.ai/threats/cve-2026-116193-rclone-from-1-64-0-before-1-75-2-contains-an-authentication)
- [rclone server-side request forgery via --rc-serve scheme-relative roots](https://junglewise.ai/threats/cve-2026-116192-rclone-from-1-37-before-1-74-2-contains-a-server-side-request)