Bug 2537399

Summary: CVE-2026-88018 rclone: rclone serve s3: --auth-proxy without --auth-key authenticates nobody - full SigV4 signature bypass [fedora-all]
Product: [Fedora] Fedora Reporter: Marian Rehak <mrehak>
Component: rcloneAssignee: Mikel Olasagasti Uranga <mikel>
Status: NEW --- QA Contact: Fedora Extras Quality Assurance <extras-qa>
Severity: urgent Docs Contact:
Priority: urgent    
Version: rawhideCC: go-sig, mikel
Target Milestone: ---Keywords: Security, SecurityTracking
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Hardware: Unspecified   
OS: Unspecified   
Whiteboard: {"flaws": ["9811b395-133d-4f8f-b886-8e14d38af816"]}
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oVirt Team: --- RHEL 7.3 requirements from Atomic Host:
Cloudforms Team: --- Target Upstream Version:
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Bug Depends On:    
Bug Blocks: 2531542    

Description Marian Rehak 2026-09-21 13:55:32 UTC 
Disclaimer: Community trackers are created by Red Hat Product Security team on a best effort basis. Package maintainers are required to ascertain if the flaw indeed affects their package, before starting the update process.

rclone is a command-line program to sync files and directories to and from different cloud storage providers. Prior to 1.75.1, rclone serve s3 configured with --auth-proxy but without --auth-key allows authPairMiddleware to register any client-chosen accessKeyID with an empty ws.s3Secret. gofakes3 then verifies the request’s SigV4 signature against that same empty secret, while Server.auth passes the access key identifier as both the user and authentication value to the proxy without an independent per-identity secret. An unauthenticated network attacker can therefore choose an arbitrary access key, sign with an empty secret, and reach whatever backend the auth-proxy script resolves for that identity. This issue is fixed in version 1.75.1.