# Cloudreve broken access control in file share caching

Source: https://junglewise.ai/threats/cloudreve-broken-access-control-in-file-share-caching-13df24a4  
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 5.3 · Published 2026-08-24

Cloudreve is a self-hosted file management and sharing platform. A former file-share recipient can generate signed download URLs for files they previously had access to for up to 5 minutes after the share is deleted or expires, bypassing the owner's revocation decision and download limits. An attacker must have already seen the files during a valid share and obtained the share hint.

Technologies: [Cloudreve](https://junglewise.ai/threats/technologies/cloudreve), [github.com/cloudreve/Cloudreve/v4 (Go)](https://junglewise.ai/threats/technologies/github-com-cloudreve-cloudreve-v4). Vendors: [Cloudreve](https://junglewise.ai/threats/vendors/cloudreve), [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 5.3, published 24 August 2026.

**Which products and versions are affected?** Cloudreve <= 4.0.0-20260606032813-26b6b1044b02; 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 web application.

**Am I affected?** Check whether you run Cloudreve or 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 is a broken access control (CWE-863) in the share-caching mechanism. The root cause spans multiple components: (1) file-listing responses return a `context_hint` (UUID) and file paths to the client; (2) the `file/url` and `file/thumb` routes accept this hint via the `X-Cr-Context-Hint` header without independent share re-validation; (3) DBFS caches `shareNavigatorState` (containing `shareRoot` and `share` row) for 300 seconds under the hint; (4) on cache hit, `shareNavigator.RestoreState` restores cached state, and `shareNavigator.To` skips calling `Root()`, which is the sole place that re-checks `inventory.IsValidShare` (expiry, download limits, owner status, source-file validity) and password; (5) failed download hooks are only logged and do not block URL generation; (6) signed content endpoints validate only the signature, not share state. An attacker who is a former recipient must pre-warm the hint cache while a share is valid, then after the owner deletes the share or it expires, can replay the cached hint within 300 seconds to obtain signed download URLs without re-authorization. Exploitation requires prior knowledge of the target file URI from a valid share listing.

## Affected products

- cloudreve Cloudreve <= 4.0.0-20260606032813-26b6b1044b02

## Timeline

- 2026-08-24: disclosed

## References

- [https://api.github.com/users/riodrwn](https://api.github.com/users/riodrwn)
- [https://github.com/riodrwn](https://github.com/riodrwn)
- [https://api.github.com/users/riodrwn/gists%7B/gist_id%7D](https://api.github.com/users/riodrwn/gists%7B/gist_id%7D)
- [https://api.github.com/users/riodrwn/repos](https://api.github.com/users/riodrwn/repos)
- [https://avatars.githubusercontent.com/u/42384611?v=4](https://avatars.githubusercontent.com/u/42384611?v=4)
- [https://api.github.com/users/riodrwn/events%7B/privacy%7D](https://api.github.com/users/riodrwn/events%7B/privacy%7D)

## Related threats

- [Cloudreve access control bypass in share validation](https://junglewise.ai/threats/cve-2026-101056-cloudreve-before-4-16-1-fails-to-revalidate-share-access-when)
- [Cloudreve authorization bypass in admin node test endpoints](https://junglewise.ai/threats/cve-2026-101048-cloudreve-before-4-17-0-registers-the-administrative-node-test)
- [Cloudreve SSRF guard bypass via IPv6 transition wrappers](https://junglewise.ai/threats/cve-2026-79913-cloudreve-ssrf-guard-bypass-via-ipv6-transition-wrappers)
- [Cloudreve privilege scope bypass in admin API endpoints](https://junglewise.ai/threats/cve-2026-77637-cloudreve-privilege-scope-bypass-in-admin-api-endpoints)
- [Cloudreve TOCTOU race in storage-quota check and charge](https://junglewise.ai/threats/cve-2026-77633-cloudreve-toctou-race-in-storage-quota-check-and-charge)