Bug 2531540 (CVE-2026-88017)

Summary: CVE-2026-88017 rclone: rclone: FTP authentication flaw allows unauthorized data access
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security <prodsec-ir-bot>
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Priority: high    
Version: unspecifiedKeywords: Security
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Hardware: All   
OS: Linux   
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A flaw was found in rclone, a command-line program for syncing files to cloud storage providers. The FTP authentication proxy driver improperly handles user credentials across sessions. If two users share the same username but are linked to different storage backends, a later login can overwrite the authentication for an active session. This allows the first session to perform unauthorized data operations, including reading, creating, or deleting files, using the second user's permissions.
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Bug Depends On: 2536988, 2536989    
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Description OSIDB Bzimport 2026-09-10 16:09:00 UTC 
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.