---
id: "CVE-2026-116187"
kind: "vulnerability"
aliases: ["CVE-2026-116187"]
title: "Rclone: S3 auth proxy lets tenants touch other tenants' multipart uploads"
severity: "medium"
cvss: 6.1
epss: null
exploited: false
status: "open"
category: "package"
products: []
ecosystems: []
tags: ["multi-tenant", "package", "rclone", "s3", "self-hosted"]
not_affected_if: ["default-config", "single-tenant"]
published_at: "2026-10-25T14:16:58+00:00"
first_seen_at: "2026-10-25T14:41:23+00:00"
updated_at: "2026-10-25T14:42:54+00:00"
sources: [{"source": "nvd", "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-116187", "first_seen_at": "2026-10-25T14:41:23+00:00"}]
---

# Rclone: S3 auth proxy lets tenants touch other tenants' multipart uploads

Rclone's serve s3 --auth-proxy mode does not check that a multipart upload ID belongs to the requesting tenant. An authenticated tenant who learns another tenant's bucket, object and upload ID can add parts, complete or abort that upload, and read upload and object metadata.

_Summary, check and fix written by a model from the sources; labelled as such._

## How to check

- Run `rclone version` and confirm the installed version is below `v1.75.2`
- Check whether the service is started with `serve s3` and `--auth-proxy` (for example in the process list or service unit)

## Fix

- Upgrade rclone to `v1.75.2` or later
- Until upgraded, stop exposing `serve s3 --auth-proxy` to tenants you do not fully trust

## Timeline

- 2026-10-25T14:41:23+00:00 nvd https://nvd.nist.gov/vuln/detail/CVE-2026-116187

## From the sources

Rclone from v1.68.0 before v1.75.2 contains an authorization bypass vulnerability in serve s3 --auth-proxy that allows authenticated tenants to manipulate other tenants' multipart uploads by referencing their upload IDs. Attackers who learn a victim's bucket, object, and upload ID can inject parts, complete, or abort in-flight uploads and view upload and object metadata across tenants.

---

_Free to read at a human pace. An API with keys and an MCP server are in preparation; early access: hello@infrastack.ai_