CVE-2026-88017 rclone: FTP cross-session auth-proxy backend confusion
An attacker can hijack an active FTP session by logging in with the same username, gaining unauthorized read and write access to another user's backend storage.
- Exploited in the wild
- Not known
- Login needed
- Any signed-in user
- Attackable
- Over the internet
- Victim action needed
- A user has to click or open something
- Fix
- Available
What is CVE-2026-88017?
CVE-2026-88017 is a high-severity authentication bypass vulnerability in rclone, published on 10 Sep 2026. Any signed-in user can exploit it over the network, and only if a user opens a file or follows a link.
Official description
rclone is a command-line program to sync files and directories to and from different cloud storage providers. From 1.64.0 until 1.75.1, the FTP auth-proxy driver in cmd/serve/ftp/ftp.go stores one obscured password per username in the server-wide userPass map[string]string instead of binding the credential or VFS to the authenticated session. If two accepted credentials use the same username but resolve to different proxy backends, a later CheckPasswd login overwrites userPass[user], and subsequent getVFS operations on the first session are reauthorized with the later password. The first session can then read, create, overwrite, rename, or delete objects using the second credential’s backend authority. Exploitation requires the later same-username login to occur while the first session remains open. This issue is fixed in version 1.75.1.
Weakness: CWE-488
Which versions are affected by CVE-2026-88017?
4 open source packages ship an affected version, including github.com/rclone/rclone and rclone. It affects 1 product.
| Package | Affected | Fixed in |
|---|---|---|
github.com/rclone/rclone Go | From 1.64.0 | 1.75.1 |
github.com/rclone/rclone Go | From 1.64.0 | 1.75.1 |
github.com/rclone/rclone Go | From 1.64.0 | 1.75.1 |
rclone Bitnami | From 1.64.0 | 1.75.1 |
Products include Rclone Rclone.
How do I fix CVE-2026-88017?
Upgrade github.com/rclone/rclone to 1.75.1 or later.
Upgrade, and rotate credentials and sessions that may have been exposed. More about Authentication bypass.
Is CVE-2026-88017 being exploited?
There is no known exploitation of CVE-2026-88017 in the wild and no public exploit code.
Other vulnerabilities in rclone
- CVE-2026-88018 rclone serve s3: --auth-proxy without --auth-key authenticates nobody - full SigV4 signature bypass
- CVE-2026-49980 Rclone: Unauthenticated command execution in `rclone rcd --rc-serve` via inline remote instantiation, bypassing CVE-2026-41179 fix
- CVE-2026-41179 RClone: Unauthenticated operations/fsinfo allows attacker-controlled backend instantiation and local command execution
- CVE-2026-41176 Rclone: Unauthenticated options/set allows runtime auth bypass, leading to sensitive operations and command execution
- CVE-2026-59733 rclone `serve restic --private-repos` authorization bypass: `..` in the URL path lets an authenticated user read, overwrite and delete other users' repositories
Sources
Also known as BIT-rclone-2026-88017, DEBIAN-CVE-2026-88017, GHSA-c476-6w5q-jw77, GO-2026-6458, MINI-2v46-23vf-4wx9, MINI-46fr-rwqx-w43c and 7 more.