# CVE-2026-62323: Cloudreve incorrect authorization in WOPI session validation

Source: https://junglewise.ai/threats/cve-2026-62323-cloudreve-incorrect-authorization-in-wopi-session-validation  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-07-31. Updated: 2026-07-31  
License: CC BY 4.0 with a link back

CVE-2026-62323 · Severity: medium · CVSS 6.3 · Published 2026-07-31

Cloudreve, a self-hosted file management and sharing system, contains a security flaw in how it handles document viewing sessions. An attacker or a compromised third-party document viewer could bypass security checks to modify files even if they were only granted permission to view them. This could lead to unauthorized data modification or loss of integrity for files stored within the system.

Technologies: [Cloudreve](https://junglewise.ai/threats/technologies/cloudreve), [github.com/cloudreve/Cloudreve (Go)](https://junglewise.ai/threats/technologies/github-com-cloudreve-cloudreve), [github.com/cloudreve/Cloudreve/v3 (Go)](https://junglewise.ai/threats/technologies/github-com-cloudreve-cloudreve-v3), [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 CVE-2026-62323 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-62323 being exploited in the wild.

**How severe is CVE-2026-62323?** Medium severity, with a CVSS score of 6.3, published 31 July 2026.

**Which products and versions are affected?** Cloudreve < 4.17.0; Cloudreve/v3 <= 3.0.0-20250225100611-da4e44b77af4; Cloudreve/v4 < 4.0.0-20260626022433-f3347130ac48; github.com/cloudreve/Cloudreve (Go) SEMVER:introduced=0; and 2 more.

**Is there a fix for CVE-2026-62323?** Yes. github.com/cloudreve/Cloudreve/v4 (Go): upgrade to 4.0.0-20260626022433-f3347130ac48 or later. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**How is CVE-2026-62323 attacked?** It is attacked over the network, in a network appliance.

**Am I affected by CVE-2026-62323?** Check whether you run Cloudreve, Cloudreve/v3, Cloudreve/v4 or one of the others listed 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/cloudreve/Cloudreve/v4 (Go): upgrade to 4.0.0-20260626022433-f3347130ac48 or later

  ```sh
  go get github.com/cloudreve/Cloudreve/v4@v4.0.0-20260626022433-f3347130ac48
  ```


## Technical details

Cloudreve's WOPI implementation fails to properly validate access tokens and session permissions in the `ViewerSessionValidation` middleware. The system generates tokens in a `<session-id>.<random-secret>` format but only validates the session ID prefix, ignoring the cryptographic secret suffix. Furthermore, the system does not persist or enforce the requested viewer action (e.g., 'view' vs 'edit') within the `ViewerSessionCache`. Consequently, an attacker with a valid view-only session ID can forge the token suffix and invoke WOPI write routes (`PutFile`, `ModifyFile`) to modify underlying files. This issue is resolved in version 4.17.0 by implementing full token comparison and session-level permission enforcement.

## Affected products

- cloudreve Cloudreve < 4.17.0

## Identifiers

- CVE-2026-62323
- GHSA-c3jm-gv5r-9wcp
- GO-2026-6104

## Timeline

- 2026-06-26: patched: Version 4.17.0 released
- 2026-07-23: advisory: GitHub Security Advisory published
- 2026-07-31: disclosed: NVD publication date

## References

- [https://github.com/cloudreve/cloudreve/commit/f3347130ac48f2ff996af9ef66c97be2dda9cba9](https://github.com/cloudreve/cloudreve/commit/f3347130ac48f2ff996af9ef66c97be2dda9cba9)
- [https://github.com/cloudreve/cloudreve/releases/tag/4.17.0](https://github.com/cloudreve/cloudreve/releases/tag/4.17.0)
- [https://github.com/cloudreve/cloudreve/security/advisories/GHSA-c3jm-gv5r-9wcp](https://github.com/cloudreve/cloudreve/security/advisories/GHSA-c3jm-gv5r-9wcp)

## 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)
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