What is the CVSS score of EUVD-2026-39018?

EUVD-2026-39018 has a contested CVSS base score of 9.8 from a third party (e.g. CISA-ADP), while the vendor rates it Critical. vuln.today uses the vendor rating as authoritative.

Which versions of rclone are affected by EUVD-2026-39018?

rclone's remote control daemon, used widely for cloud storage synchronization, contains an unauthenticated remote code execution vulnerability in versions 1.55.0-1.74.2; while no public exploit has…. A patch is available.

How to fix or mitigate EUVD-2026-39018?

Within 24 hours: Identify all rclone deployments using --rc-serve; verify HTTP authentication is enabled; if the remote control daemon is exposed without authentication, immediately restrict network access to trusted internal networks only or disable --rc-serve. Within 7 days: Document all rclone instances, assess exposure risk to untrusted networks, and implement network segmentation to isolate systems. Within 30 days: Monitor rclone release notes for vendor patch; execute immediate upgrade to patched version once available; evaluate alternative solutions if remote control daemon cannot be adequately secured.

rclone EUVD-2026-39018

| CVE-2026-49980 CRITICAL

Missing Authentication for Critical Function (CWE-306)

2026-06-16 https://github.com/rclone/rclone

GHSA-qw24-gh76-8rvv

Authentication Bypass Mozilla

Critical

Disputed · 9.8 Vendor: https://github.com/rclone/rclone

Severity by source

Sources disagree (Medium–Critical)

Vendor (https://github.com/rclone/rclone) PRIMARY

9.8 CRITICAL

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

vuln.today AI

9.8 CRITICAL

Network-reachable rc listener with no authentication when `--rc-serve` is set yields PR:N/UI:N/AC:L; arbitrary command execution as the rclone user gives C/I/A:H.

3.1 AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

4.0 AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N

SUSE

MEDIUM

qualitative

Red Hat

9.8 CRITICAL

qualitative

vuln.today treats the vendor’s rating as authoritative. A higher third-party CVSS (e.g. CISA-ADP) is shown for transparency but does not drive the headline severity.

CVSS VectorVendor: https://github.com/rclone/rclone

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

Attack Vector

Network

Attack Complexity

Low

Privileges Required

None

User Interaction

None

Scope

Unchanged

Confidentiality

High

Integrity

High

Availability

High

Lifecycle Timeline

Source Code Evidence Fetched

Jun 17, 2026 - 00:16 vuln.today

Analysis Generated

Jun 17, 2026 - 00:16 vuln.today

CVE Published

Jun 16, 2026 - 23:39 github-advisory

CRITICAL 9.8

DescriptionCVE.org

Summary

rclone rcd --rc-serve accepts unauthenticated GET and HEAD requests to paths of the form:

text

/[remote:path]/object

The remote value is parsed from the URL and passed to normal backend initialization. Inline remote configuration can set backend options that execute local commands during initialization. As a result, a single unauthenticated GET or HEAD request can execute a command as the rclone process user.

Versions from 1.55.0 onwards are vulnerable to command execution. Earlier versions (from 1.46.0) are vulnerable to the unauthenticated local file read described under "Additional impact" but not to command execution, because inline backend option overrides did not exist until 1.55.0.

Preconditions

Preconditions for this vulnerability are:

The rclone remote control API must be enabled, either by the --rc flag or by running the rclone rcd server
The remote control API must be reachable by the attacker - by default rclone only serves the rc to localhost unless the --rc-addr flag is in use
The rc must have been deployed without global RC HTTP authentication - so not using --rc-user/--rc-pass/--rc-htpasswd/etc
The --rc-serve flag must be in use

Impact

An unauthenticated network attacker who can reach the RC HTTP listener can execute commands as the rclone process user.

Additional impact observed during testing:

GET and HEAD both trigger backend initialization.
The same path allows unauthenticated local file read through inline local remotes.
Inline global.* options can mutate process-wide rclone configuration, including global.http_proxy.
Browser subresource requests can also trigger the issue against a localhost-only RC listener. In testing, Firefox triggered the payload from a public HTTPS page containing only an <img> tag pointing at http://127.0.0.1:5572/.... This is an additional impact multiplier, not the primary attack precondition.

Mitigations / Workarounds

Upgrade to rclone 1.74.3 (or 1.75.0 when released).
Or, configure HTTP authentication on the rc with --rc-user/--rc-pass

or --rc-htpasswd, which has always been the recommended deployment.

Or, do not use --rc-serve if file serving is not needed.

The Fix

The vulnerabilities in this advisory have been fixed by two commits:

rc: fix unauthenticated command execution via --rc-serve inline remotes
rc: stop global.* connection string options changing config

Articles & Coverage 1

News Critical RCE in Mozilla - CVE-2026-49980 Jun 17, 2026

AnalysisAI

Unauthenticated remote command execution in rclone's remote control daemon (rcd) affects versions 1.55.0 through 1.74.2 when started with --rc-serve and without HTTP authentication. A single GET or HEAD request to /[remote:path]/object triggers backend initialization with attacker-controlled inline remote options, executing commands as the rclone process user. No public exploit identified at time of analysis, though the GHSA advisory describes the technique in detail and notes the issue bypasses the earlier CVE-2026-41179 fix.

Technical ContextAI

rclone is a widely used Go-based command-line program for syncing files to and from cloud storage backends. Its optional remote control (rc) HTTP API, enabled with --rc or the rclone rcd subcommand, exposes management endpoints; the --rc-serve flag additionally turns paths like /[remote:path]/object into file-serving endpoints. The server parses the bracketed remote segment from the URL and passes it into rclone's normal backend initialization path, where connection-string syntax allows inline option overrides. From rclone 1.55.0 onward, backend options can include directives that spawn local commands during initialization, turning a URL parameter into a command sink. The root cause maps to CWE-306 (Missing Authentication for a Critical Function): a code path that loads arbitrary backend configuration and runs commands is reachable on a listener that performs no authentication when HTTP auth flags are absent. Affected package is pkg:go/github.com/rclone/rclone.

RemediationAI

Vendor-released patch: upgrade to rclone 1.74.3 (or 1.75.0 when released) per advisory GHSA-qw24-gh76-8rvv (https://github.com/rclone/rclone/security/advisories/GHSA-qw24-gh76-8rvv). If immediate upgrade is not possible, enable HTTP authentication on the rc listener via --rc-user/--rc-pass or --rc-htpasswd, which has always been the recommended deployment and blocks the unauthenticated path entirely (trade-off: any existing automation calling the rc must be updated with credentials). Alternatively, drop the --rc-serve flag if file serving is not required - this disables the vulnerable path-based file endpoints but preserves the rest of the rc API (trade-off: clients depending on /[remote:path]/object HTTP file serving will break). Avoid binding the rc to non-localhost interfaces with --rc-addr until patched, and where possible block outbound browsers from reaching the rcd port to mitigate the browser-subresource pivot.