Detect Rclone RCD Unauthenticated Command Execution via Inline Remote Instantiation (CVE-2026-49980) in Elastic Security
CVE-2026-49980 is a critical unauthenticated remote code execution vulnerability in Rclone versions 1.46.0 through 1.74.2. When the rclone remote control daemon (rcd) is started with the --rc-serve flag, an attacker can instantiate arbitrary remotes inline via the RC API without authentication, bypassing the fix introduced for CVE-2026-41179. This allows execution of arbitrary commands on the host running rclone rcd. CVSS 9.8. PoC is publicly available.
MITRE ATT&CK
Elastic Detection Query
sequence by host.name with maxspan=5m
[process where event.type == "start"
and process.name : ("rclone", "rclone.exe")
and (process.args : "rcd" or process.args : "--rc-serve" or process.command_line : "*rc-serve*")]
[network where event.type == "connection"
and (destination.port == 5572 or source.port == 5572)]EQL sequence correlation: detects rclone launched with rcd/rc-serve flags shortly followed by a network event on port 5572, suggesting exploitation of CVE-2026-49980.
Data Sources
Required Tables
False Positives & Tuning
- Legitimate rclone rcd usage for internal automation with authentication enabled
- Container orchestration environments that expose rclone rcd on non-default ports
- Monitoring agents that connect to rclone RC API for health checks
Other platforms for CVE-2026-49980
Testing Methodology
Validate this detection against 3 adversary techniques from Atomic Red Team. Each test below lists the behaviour to exercise and the telemetry you should expect to see. Executable commands and cleanup steps are available with Pro.
- Test 1Unauthenticated rclone rcd RC API probe
Expected signal: Process creation event for rclone with arguments including rcd and --rc-no-auth; network bind event on port 5572; outbound HTTP POST to 127.0.0.1:5572
- Test 2Inline remote instantiation via unauthenticated RC API
Expected signal: HTTP POST to /config/create on port 5572; rclone process spawned with --rc-no-auth; possible rclone.conf modification event
- Test 3Remote command execution via rclone RC /core/command endpoint
Expected signal: HTTP POST to /core/command; rclone process with --rc-no-auth flag in process tree; network event on port 5572 from unexpected source
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