Auth bypass in Rclone

CVE-2026-88044

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.

Vulnerability class: Broken Access Control

Published · last modified .

CVSS v3 metric

CVSS v3 base score 9.1 (Critical). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N.

EPSS exploit prediction

EPSS: 0.005 (42.0th percentile), scored .

Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 42nd percentile — 42.0% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS trend (30 days)EPSS over the last 30 days for CVE-2026-88044: held from 0.006 to 0.005.

EPSS over last 30 days · oldest: 0.006 · newest: 0.005 · change: -0.001

Affected products

  • Rclone — versions >= 1.70.0, < 1.75.1

Weakness classification (CWE)

References

Frequently asked questions

What is CVE-2026-88044?
CVE-2026-88044 is a critical-severity vulnerability in Rclone, classified under Incorrect Authorization. CVSS score: 9.1/10. Published 2026-09-10.
How severe is CVE-2026-88044?
Critical severity. CVSS v3 base score is 9.1 out of 10.