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Rclone 1.70.x < 1.75.1 RC Per-Server Auth-Proxy Bypass (CVE-2026-88044)

critical Nessus Plugin ID 346828

Synopsis

An application installed on the remote host is affected by an authentication bypass vulnerability.

Description

The version of Rclone installed on the remote host is 1.70.x prior to 1.75.1. It is, therefore, affected by an authentication bypass vulnerability:

 - The serve/start remote control method accepts protocol options in a per-server proxyOpt object, but the FTP and S3 server constructors decide whether proxy authentication is enabled by checking the process-global proxy.Opt.AuthProxy instead of the supplied proxyOpt.AuthProxy.
 When the process-global option is empty, the supplied authentication proxy is silently ignored and FTP falls back to its fixed-backend mode, whose defaults accept the username anonymous with any password, exposing read, write, and delete operations without the authentication the operator configured. For S3, an accepted key reaches the fixed filesystem rather than the backend the auth proxy would have selected. (CVE-2026-88044)

Note that Nessus has not tested for this issue but has instead relied only on the application's self-reported version number.

Solution

Upgrade to Rclone version 1.75.1 or later.

See Also

https://github.com/rclone/rclone/releases/tag/v1.75.1

http://www.nessus.org/u?cefc3678

Plugin Details

Severity: Critical

ID: 346828

File Name: rclone_CVE-2026-88044.nasl

Version: 1.2

Type: Local

Agent: windows, macosx, unix

Family: Misc.

Published: 9/17/2026

Updated: 9/18/2026

Configuration: Enable thorough checks (optional)

Supported Sensors: Nessus Agent, Nessus

Risk Information

VPR

Risk Factor: Medium

Score: 4.3

Percentile: 53.47

CVSS v2

Risk Factor: High

Base Score: 9.4

Temporal Score: 7

Vector: CVSS2#AV:N/AC:L/Au:N/C:C/I:C/A:N

CVSS Score Source: CVE-2026-88044

CVSS v3

Risk Factor: Critical

Base Score: 9.1

Temporal Score: 7.9

Vector: CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N

Temporal Vector: CVSS:3.0/E:U/RL:O/RC:C

Vulnerability Information

CPE: cpe:/a:rclone:rclone

Required KB Items: installed_sw/rclone

Exploit Ease: No known exploits are available

Patch Publication Date: 9/4/2026

Vulnerability Publication Date: 9/10/2026

Reference Information

CVE: CVE-2026-88044