# CVE-2026-79781: rclone serve s3 path traversal via dot-dot object keys

Source: https://junglewise.ai/threats/cve-2026-79781-rclone-serve-s3-path-traversal-via-dot-dot-object-keys  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-08-25. Updated: 2026-09-25  
License: CC BY 4.0 with a link back

CVE-2026-79781 · Severity: medium · CVSS 6.5 · Published 2026-08-25

rclone serve s3 is a local S3-compatible server component used to expose file directories over the S3 protocol. A path traversal vulnerability allows remote attackers to read and overwrite files at the root level of the served directory by using ".." segments in S3 object key names, bypassing bucket namespace isolation and potentially exposing or modifying sensitive files.

Technologies: [github.com/rclone/rclone (Go)](https://junglewise.ai/threats/technologies/github-com-rclone-rclone), [Rclone](https://junglewise.ai/threats/technologies/rclone). Vendors: [Go](https://junglewise.ai/threats/vendors/go), [Rclone](https://junglewise.ai/threats/vendors/rclone).

## Quick answers

**Is CVE-2026-79781 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-79781 being exploited in the wild.

**How severe is CVE-2026-79781?** Medium severity, with a CVSS score of 6.5, published 25 August 2026.

**Which products and versions are affected?** github.com/rclone/rclone (Go) SEMVER:introduced=0,fixed=1.74.4; Rclone before 1.74.4.

**Is there a fix for CVE-2026-79781?** Yes. github.com/rclone/rclone (Go): upgrade to 1.74.4 or later. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**How is CVE-2026-79781 attacked?** It is attacked over the network, in a hosted service.

**Am I affected by CVE-2026-79781?** Check whether you run github.com/rclone/rclone (Go) or Rclone at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## How to fix

- github.com/rclone/rclone (Go): upgrade to 1.74.4 or later

  ```sh
  go get github.com/rclone/rclone@v1.74.4
  ```


## Technical details

The vulnerability is a path traversal / improper path normalization flaw in the S3 backend layer (cmd/serve/s3/backend.go). The root cause is use of Go's path.Join() function, which normalizes ".." segments as filesystem-style path components, on opaque S3 object keys that should be treated literally. An attacker can craft S3 requests with object keys such as "../root-secret.txt" to escape the bucket namespace; when path.Join("bucket", "../root-secret.txt") is evaluated, it resolves to "root-secret.txt" in the serve root directory. The vulnerability affects GET (read), PUT (write), and DELETE operations, and requires only network reachability—no authentication is required when the server is run without --auth-key. The fix is available in rclone version 1.74.4 and later.

## Affected products

- rclone rclone before 1.74.4

## Identifiers

- CVE-2026-79781
- GHSA-8v25-v8p6-qf7v
- GO-2026-6189

## Timeline

- 2026-07-08: disclosed: GitHub Security Advisory GHSA-8v25-v8p6-qf7v published
- 2026-08-25: advisory: CVE-2026-79781 published on NVD
- 2026: patched: Fix available in rclone 1.74.4

## References

- [https://github.com/rclone/rclone/security/advisories/GHSA-8v25-v8p6-qf7v](https://github.com/rclone/rclone/security/advisories/GHSA-8v25-v8p6-qf7v)
- [https://www.vulncheck.com/advisories/rclone-serve-s3-path-traversal-via-dot-dot-object-keys](https://www.vulncheck.com/advisories/rclone-serve-s3-path-traversal-via-dot-dot-object-keys)

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