https://feed.craftedsignal.io/tags/rclone/Trending threats, MITRE ATT&CK coverage, and detection metadata — refreshed continuously.Hugoenhello@craftedsignal.iohello@craftedsignal.ioMon, 04 May 2026 14:17:05 +0000https://feed.craftedsignal.io/briefs/2026-05-rclone-exfiltration/Mon, 04 May 2026 14:17:05 +0000hello@craftedsignal.iohttps://feed.craftedsignal.io/briefs/2026-05-rclone-exfiltration/Attackers are abusing the legitimate file synchronization tool rclone, often renamed to masquerade as legitimate software, to exfiltrate data to cloud storage or remote endpoints.Attackers are leveraging Rclone, a legitimate command-line program to manage files on cloud storage, for malicious purposes. The primary abuse case involves renaming Rclone (e.g., to TrendFileSecurityCheck.exe) to evade detection based on process name. Once renamed, attackers use Rclone’s copy/sync functionalities with cloud backends like S3 or HTTP endpoints. They often employ --include filters to target specific sensitive file types for exfiltration. This activity is frequently blended with regular administrative traffic to further obfuscate the malicious intent. Defenders should be aware of this tactic, particularly when unusual processes are observed interacting with cloud storage services.

Attack Chain

1. The attacker gains initial access to the system through an undisclosed method.
2. Rclone is downloaded or transferred to the victim machine.
3. The rclone executable is renamed to a benign-sounding name (e.g., TrendFileSecurityCheck.exe) to masquerade as a legitimate system utility.
4. The attacker configures rclone to connect to a cloud storage backend (e.g., an S3 bucket or HTTP endpoint) controlled by the attacker.
5. A command is executed using the renamed rclone executable, specifying the copy or sync command.
6. The command includes --include flags to filter and select specific file types (e.g., documents, source code, databases) for exfiltration.
7. Rclone transfers the targeted files from the victim machine to the attacker’s cloud storage backend, potentially using the --transfers option for faster exfiltration.
8. The attacker accesses the exfiltrated data from their cloud storage.

Impact

Successful exploitation can lead to the exfiltration of sensitive data, including proprietary information, customer data, financial records, or intellectual property. The impact can range from reputational damage and financial losses to legal and regulatory repercussions. The scope of damage depends on the sensitivity and volume of the exfiltrated data, the number of affected systems, and the effectiveness of the attacker’s filtering criteria.

Recommendation

• Deploy the Sigma rule Suspicious Rclone Usage to detect renamed rclone executables executing copy/sync commands.
• Enable Sysmon process creation logging (Event ID 1) to collect the necessary process execution data for the Sigma rules.
• Investigate any process identified by the Sigma rule Suspicious Rclone Usage by examining command-line arguments for cloud backend destinations and --include filters.
• Monitor network connections for unusual outbound traffic to cloud storage providers (AWS S3, Azure Blob Storage, Google Cloud Storage) from processes other than approved backup solutions.
• Implement application control policies to restrict the execution of unauthorized or renamed executables.

]]>mediumadvisorydata-exfiltrationrclonemasqueradinghttps://feed.craftedsignal.io/briefs/2026-04-rclone-auth-bypass/Thu, 23 Apr 2026 12:00:00 +0000hello@craftedsignal.iohttps://feed.craftedsignal.io/briefs/2026-04-rclone-auth-bypass/Rclone is vulnerable to an unauthenticated options/set vulnerability that allows runtime authentication bypass, potentially leading to sensitive operations and command execution by setting `rc.NoAuth=true` on reachable RC servers started without global HTTP authentication.Rclone, a command-line program to manage files on cloud storage, is vulnerable to an authentication bypass via its remote control (RC) API. The vulnerability, present from version 1.45 onwards, stems from the options/set endpoint being exposed without authentication requirements, while still being able to modify the global runtime configuration. An unauthenticated attacker can exploit this vulnerability by setting the rc.NoAuth parameter to true, effectively disabling the authentication gate for numerous RC methods registered with AuthRequired: true. This allows unauthorized access to sensitive administrative functionality, including configuration settings and operational commands. The issue was validated against v1.73.4 and the current master branch as of April 14, 2026. This vulnerability is especially critical when the RC API is exposed without global HTTP authentication (i.e. --rc-user/--rc-pass are not set), as it allows complete control of the Rclone instance.

Attack Chain

1. An attacker identifies a vulnerable Rclone instance with the RC API enabled (via --rc or rclone rcd) that is reachable on the network. The attacker confirms that the RC API is not protected by global HTTP authentication (no --rc-user, --rc-pass, or --rc-htpasswd flags).
2. The attacker sends an unauthenticated POST request to the /options/set endpoint with a JSON payload setting rc.NoAuth to true: {"rc":{"NoAuth":true}}.
3. The Rclone RC server processes the request and updates the runtime configuration, disabling the authentication requirement for subsequent RC calls.
4. The attacker leverages the now-unprotected RC API to access sensitive configuration data using endpoints like /config/listremotes, /config/dump, or /config/get.
5. The attacker can list the available filesystems and remote configurations.
6. The attacker then uses operational endpoints such as /operations/list to list files and directories within a configured remote.
7. The attacker exploits the /operations/copyfile endpoint to copy files from one location to another, potentially exfiltrating sensitive data or overwriting critical files.
8. Finally, the attacker uses the /core/command endpoint to execute arbitrary commands on the host system, achieving complete system compromise. This endpoint utilizes the exec.Command(...) function, allowing arbitrary command execution.

Impact

Successful exploitation of this vulnerability allows an unauthenticated attacker to bypass intended access controls on the Rclone RC administrative interface. The impact ranges from sensitive configuration disclosure and filesystem enumeration to arbitrary command execution on the host system. This could lead to complete system compromise, data exfiltration, or denial of service. The vulnerability affects Rclone instances from version 1.45 up to (but not including) 1.73.5. The severity is amplified when the RC API is exposed to a wider network without proper authentication measures.

Recommendation

• Upgrade Rclone to version 1.73.5 or later to patch CVE-2026-41176.
• If upgrading is not immediately feasible, ensure that the Rclone RC API is protected by global HTTP authentication using the --rc-user, --rc-pass, or --rc-htpasswd flags.
• Monitor network traffic for POST requests to the /options/set endpoint without authentication, indicative of exploitation attempts. Deploy the provided Sigma rule to detect this activity.
• Review Rclone RC API access logs for unauthorized access to sensitive endpoints such as /config/listremotes, /config/dump, /config/get, /operations/list, /operations/copyfile, and /core/command after the /options/set endpoint has been accessed.

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