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CVE-2026-88017— rclone: FTP cross-session auth-proxy backend confusion

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 是一个用于在不同云存储提供商之间同步文件和目录的命令行程序。 在 1.64.0 至 1.75.1 版本中， 中的 FTP 认证代理驱动存在一个缺陷：它针对每个用户名在服务器级的 映射（ ）中只存储一个被混淆的密码，而不是将凭证或 VFS（虚拟文件系统）绑定到已认证的会话。 如果两个被接受的凭证使用相同的用户名但解析到不同的代理后端，那么后续使用相同用户名进行的 登录会覆盖 ，导致第一个会话中后续的 操作会改用后一个密码进行重新授权。这样一来，第一个会话就可以使用第二个凭证的后端权限来读取、创建、覆盖、

CVSS 7.3 · High
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I. Basic Information for CVE-2026-88017

Vulnerability Information
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Vulnerability Title
rclone: FTP cross-session auth-proxy backend confusion
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 1.64.0 until 1.75.1, the FTP auth-proxy driver in cmd/serve/ftp/ftp.go stores one obscured password per username in the server-wide userPass map[string]string instead of binding the credential or VFS to the authenticated session. If two accepted credentials use the same username but resolve to different proxy backends, a later CheckPasswd login overwrites userPass[user], and subsequent getVFS operations on the first session are reauthorized with the later password. The first session can then read, create, overwrite, rename, or delete objects using the second credential’s backend authority. Exploitation requires the later same-username login to occur while the first session remains open. 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:L/UI:R/S:U/C:H/I:H/A:N
Source: CVE Program / CVE List V5
Vulnerability Type
对错误会话暴露数据元素
Source: CVE Program / CVE List V5

Affected Products

Vendor Product Affected Versions CPE Subscribe
rclone rclone >= 1.64.0, < 1.75.1 -

II. Public POCs for CVE-2026-88017

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III. Intelligence Information for CVE-2026-88017

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Other References for CVE-2026-88017 (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-2026-88044 9.1 CRITICAL rclone: RC per-server auth-proxy bypass
CVE-2026-88045 7.5 HIGH rclone: S3 multipart declared-length memory exhaustion
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-488

V. Comments for CVE-2026-88017

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