# Cloudreve path traversal in remote download

Source: https://junglewise.ai/threats/cloudreve-path-traversal-in-remote-download-28748249  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-08-24. Updated: 2026-09-25  
License: CC BY 4.0 with a link back

Severity: medium · CVSS 5.5 · Published 2026-08-24

Cloudreve is a self-hosted cloud storage system that supports remote file downloads via external downloaders like aria2. A vulnerability in how Cloudreve processes file paths from these remote downloaders allows attackers to cause downloaded files to be placed outside the intended folder structure using path traversal sequences like `../../`. An attacker with remote-download privileges could exploit this to write files to unintended locations in their accessible storage namespace, potentially overwriting files or bypassing organizational folder controls.

Technologies: [github.com/cloudreve/Cloudreve/v4 (Go)](https://junglewise.ai/threats/technologies/github-com-cloudreve-cloudreve-v4). Vendors: [Go](https://junglewise.ai/threats/vendors/go).

## Quick answers

**Is This vulnerability exploited in the wild?** No. Junglewise Threat Intelligence has no report of This vulnerability being exploited in the wild.

**How severe is This vulnerability?** Medium severity, with a CVSS score of 5.5, published 24 August 2026.

**Which products and versions are affected?** github.com/cloudreve/Cloudreve/v4 (Go) <= 4.0.0-20260606032813-26b6b1044b02.

**Is there a fix for This vulnerability?** No fixed version is recorded yet. Check the vendor's advisory in the references below. If you run it, Junglewise drafts a mitigation that fits your setup and applies it once you approve, with senior security engineers behind it.

**How is This vulnerability attacked?** It is attacked over the network, in a software library.

**Am I affected?** Check whether you run github.com/cloudreve/Cloudreve/v4 (Go) 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.

## Technical details

The vulnerability exists in the remote download workflow (pkg/filemanager/workflows/remote_download.go) where Cloudreve combines a user-selected destination URI with a downloader-reported file name using the JoinRaw() function. The sanitizeFileName() function only replaces backslashes and special Windows characters (`:*?"<>|`) with underscores, but does not filter forward slashes or parent directory references (`..`). The JoinRaw() function then processes these unfiltered path segments, allowing `..` sequences to traverse up the directory tree. For aria2 downloads, the file name is extracted from the aria2 API response (aria2.tellStatus().files[].path), which is not validated before joining with the destination path. An authenticated user with remote-download permission can trigger this by creating a download task if the configured downloader returns a malicious path. The resulting file placement is subject to Cloudreve's existing upload and permission checks, limiting write scope to the user's accessible namespace.

## Affected products

- Cloudreve Cloudreve <= 4.0.0-20260606032813-26b6b1044b02

## Timeline

- 2026-06-13: disclosed: Published to GitHub Advisory Database
- 2026-08-24: advisory: GHSA-w8j7-39hp-8x59 published

## References

- [https://api.github.com/users/jinhao-huang](https://api.github.com/users/jinhao-huang)
- [https://github.com/jinhao-huang](https://github.com/jinhao-huang)
- [https://api.github.com/users/jinhao-huang/gists%7B/gist_id%7D](https://api.github.com/users/jinhao-huang/gists%7B/gist_id%7D)
- [https://api.github.com/users/jinhao-huang/repos](https://api.github.com/users/jinhao-huang/repos)
- [https://avatars.githubusercontent.com/u/80573215?v=4](https://avatars.githubusercontent.com/u/80573215?v=4)
- [https://api.github.com/users/jinhao-huang/events%7B/privacy%7D](https://api.github.com/users/jinhao-huang/events%7B/privacy%7D)

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