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CVE-2026-88044— rclone: RC per-server auth-proxy bypass

Quick assessment

Affected
rclone rclone
Exploitation
No confirmed in-the-wild exploitation; assess based on exposure
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

rclone 是一款命令行工具，用于在不同的云存储提供商之间同步文件和目录。从 1.70.0 到 1.75.1 版本中， / RC 接口本应接受按服务器配置的 设置，但 和 中的 FTP 和 S3 构造函数错误地检查了进程级的全局 值。当全局值为空时，请求本地的认证代理配置会被忽略：FTP 服务会回退到固定的文件系统，允许使用用户名 和任意密码进行访问；而 S3 服务在启用 时，会返回固定的 RC 文件系统，而不是由代理选定的后端存储。专门用于配置全局选项的命令行服务器不受此问题影响。该问题已在 1.75.1 版本

CVSS 9.1 · Critical

Possible ATT&CK Techniques 1 AI

T1557 · Adversary-in-the-Middle
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I. Basic Information for CVE-2026-88044

Vulnerability Information
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Vulnerability Title
rclone: RC per-server auth-proxy bypass
Source: CVE Program / CVE List V5
Vulnerability Description
rclone is a command-line program to sync files and directories to and from different cloud storage providers. From 1.70.0 until 1.75.1, the serve/start RC interface accepts per-server proxyOpt.AuthProxy settings, and the FTP and S3 constructors in cmd/serve/ftp/ftp.go and cmd/serve/s3/server.go incorrectly check the process-global proxy.Opt.AuthProxy value instead. When the global value is empty, the request-local authentication proxy is ignored: FTP falls back to the fixed filesystem with username anonymous and any password, while S3 with AuthKey serves the fixed RC fs rather than the backend selected by the proxy. The dedicated command-line servers that configure the global option are not affected. This issue is fixed in version 1.75.1.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N
Source: CVE Program / CVE List V5
Vulnerability Type
授权机制不正确
Source: CVE Program / CVE List V5

Affected Products

Vendor Product Affected Versions CPE Subscribe
rclone rclone >= 1.70.0, < 1.75.1 -

II. Public POCs for CVE-2026-88044

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III. Intelligence Information for CVE-2026-88044

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Other References for CVE-2026-88044 (2)

Same Patch Batch · rclone · 2026-09-10 · 9 CVEs total

CVE-2026-88018 9.8 CRITICAL rclone serve s3: --auth-proxy without --auth-key authenticates nobody - full SigV4 signatu
CVE-2026-88045 7.5 HIGH rclone: S3 multipart declared-length memory exhaustion
CVE-2026-88017 7.3 HIGH rclone: FTP cross-session auth-proxy backend confusion
CVE-2026-88016 7.1 HIGH rclone: Directory metadata (chmod/chown/chtimes) applied through a planted symlink in rclo
CVE-2026-88014 6.3 MEDIUM rclone archive/zip: Zip Slip via unsanitized zip entry names lets a malicious archive esca
CVE-2026-88015 5.3 MEDIUM rclone local: crafted Range request against a translated symlink panics (DoS)
CVE-2026-88046 5.3 MEDIUM rclone: source object names can escape the configured root on upload
CVE-2026-88013 3.7 LOW rclone: http backend forwards custom/auth headers to a different host on redirect

IV. Related Vulnerabilities

Same product: rclone
Same vendor: rclone
Same weakness: CWE-863

V. Comments for CVE-2026-88044

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