{"description":"Trending threats, MITRE ATT\u0026CK coverage, and detection metadata — refreshed continuously.","feed_url":"https://feed.craftedsignal.io/tags/auth-bypass/","home_page_url":"https://feed.craftedsignal.io/","items":[{"_cs_actors":[],"_cs_cves":[],"_cs_exploited":false,"_cs_products":["rclone"],"_cs_severities":["critical"],"_cs_tags":["rclone","auth-bypass","rc-api","CVE-2026-41176","command-execution"],"_cs_type":"advisory","_cs_vendors":["rclone"],"content_html":"\u003cp\u003eRclone, 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 \u003ccode\u003eoptions/set\u003c/code\u003e 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 \u003ccode\u003erc.NoAuth\u003c/code\u003e parameter to \u003ccode\u003etrue\u003c/code\u003e, effectively disabling the authentication gate for numerous RC methods registered with \u003ccode\u003eAuthRequired: true\u003c/code\u003e. This allows unauthorized access to sensitive administrative functionality, including configuration settings and operational commands. The issue was validated against \u003ccode\u003ev1.73.4\u003c/code\u003e and the current \u003ccode\u003emaster\u003c/code\u003e branch as of April 14, 2026. This vulnerability is especially critical when the RC API is exposed without global HTTP authentication (i.e. \u003ccode\u003e--rc-user\u003c/code\u003e/\u003ccode\u003e--rc-pass\u003c/code\u003e are not set), as it allows complete control of the Rclone instance.\u003c/p\u003e\n\u003ch2 id=\"attack-chain\"\u003eAttack Chain\u003c/h2\u003e\n\u003col\u003e\n\u003cli\u003eAn attacker identifies a vulnerable Rclone instance with the RC API enabled (via \u003ccode\u003e--rc\u003c/code\u003e or \u003ccode\u003erclone rcd\u003c/code\u003e) that is reachable on the network. The attacker confirms that the RC API is not protected by global HTTP authentication (no \u003ccode\u003e--rc-user\u003c/code\u003e, \u003ccode\u003e--rc-pass\u003c/code\u003e, or \u003ccode\u003e--rc-htpasswd\u003c/code\u003e flags).\u003c/li\u003e\n\u003cli\u003eThe attacker sends an unauthenticated POST request to the \u003ccode\u003e/options/set\u003c/code\u003e endpoint with a JSON payload setting \u003ccode\u003erc.NoAuth\u003c/code\u003e to \u003ccode\u003etrue\u003c/code\u003e: \u003ccode\u003e{\u0026quot;rc\u0026quot;:{\u0026quot;NoAuth\u0026quot;:true}}\u003c/code\u003e.\u003c/li\u003e\n\u003cli\u003eThe Rclone RC server processes the request and updates the runtime configuration, disabling the authentication requirement for subsequent RC calls.\u003c/li\u003e\n\u003cli\u003eThe attacker leverages the now-unprotected RC API to access sensitive configuration data using endpoints like \u003ccode\u003e/config/listremotes\u003c/code\u003e, \u003ccode\u003e/config/dump\u003c/code\u003e, or \u003ccode\u003e/config/get\u003c/code\u003e.\u003c/li\u003e\n\u003cli\u003eThe attacker can list the available filesystems and remote configurations.\u003c/li\u003e\n\u003cli\u003eThe attacker then uses operational endpoints such as \u003ccode\u003e/operations/list\u003c/code\u003e to list files and directories within a configured remote.\u003c/li\u003e\n\u003cli\u003eThe attacker exploits the \u003ccode\u003e/operations/copyfile\u003c/code\u003e endpoint to copy files from one location to another, potentially exfiltrating sensitive data or overwriting critical files.\u003c/li\u003e\n\u003cli\u003eFinally, the attacker uses the \u003ccode\u003e/core/command\u003c/code\u003e endpoint to execute arbitrary commands on the host system, achieving complete system compromise. This endpoint utilizes the \u003ccode\u003eexec.Command(...)\u003c/code\u003e function, allowing arbitrary command execution.\u003c/li\u003e\n\u003c/ol\u003e\n\u003ch2 id=\"impact\"\u003eImpact\u003c/h2\u003e\n\u003cp\u003eSuccessful 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.\u003c/p\u003e\n\u003ch2 id=\"recommendation\"\u003eRecommendation\u003c/h2\u003e\n\u003cul\u003e\n\u003cli\u003eUpgrade Rclone to version 1.73.5 or later to patch CVE-2026-41176.\u003c/li\u003e\n\u003cli\u003eIf upgrading is not immediately feasible, ensure that the Rclone RC API is protected by global HTTP authentication using the \u003ccode\u003e--rc-user\u003c/code\u003e, \u003ccode\u003e--rc-pass\u003c/code\u003e, or \u003ccode\u003e--rc-htpasswd\u003c/code\u003e flags.\u003c/li\u003e\n\u003cli\u003eMonitor network traffic for POST requests to the \u003ccode\u003e/options/set\u003c/code\u003e endpoint without authentication, indicative of exploitation attempts. Deploy the provided Sigma rule to detect this activity.\u003c/li\u003e\n\u003cli\u003eReview Rclone RC API access logs for unauthorized access to sensitive endpoints such as \u003ccode\u003e/config/listremotes\u003c/code\u003e, \u003ccode\u003e/config/dump\u003c/code\u003e, \u003ccode\u003e/config/get\u003c/code\u003e, \u003ccode\u003e/operations/list\u003c/code\u003e, \u003ccode\u003e/operations/copyfile\u003c/code\u003e, and \u003ccode\u003e/core/command\u003c/code\u003e after the \u003ccode\u003e/options/set\u003c/code\u003e endpoint has been accessed.\u003c/li\u003e\n\u003c/ul\u003e\n","date_modified":"2026-04-23T12:00:00Z","date_published":"2026-04-23T12:00:00Z","id":"/briefs/2026-04-rclone-auth-bypass/","summary":"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.","title":"Rclone Unauthenticated options/set Allows Runtime Auth Bypass","url":"https://feed.craftedsignal.io/briefs/2026-04-rclone-auth-bypass/"}],"language":"en","title":"CraftedSignal Threat Feed — Auth-Bypass","version":"https://jsonfeed.org/version/1.1"}