CVE-2026-62323

Cloudreve WOPI view sessions can write files and WOPI access token secret is ignored

A WOPI integration that is only expected to view a user's file can modify that file through the WOPI write endpoints. If the WOPI URL or session id leaks, the random token suffix does not protect the session because any suffix is accepted for an existing session id.

This affects deployments that configure WOPI viewers for user files. The attacker primitive is strongest when a malicious or compromised WOPI viewer receives a view-only URL and then writes content back to Cloudreve.

The application does not correctly enforce access controls, allowing a principal to access resources or operations beyond their granted permissions. Typical impact: unauthorized data access or execution of privileged operations.

CVE-2026-62323 has a CVSS score of 6.3 (Medium). The vector is network-reachable, low privileges required, and user interaction required. A CVSS score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether this affects your application depends on whether the vulnerable code is present and reachable in your environment. A fixed version is available (4.0.0-20260626022433-f3347130ac48); upgrading removes the vulnerable code path.

Kodem intelligence

Already deployed Kodem?

• Compare the full supplied access_token to the stored ViewerSessionCache.Token using constant-time comparison.
• Reject malformed tokens and tokens with extra separators.
• Store a CanWrite flag or selected WOPI action in ViewerSessionCache.
• Enforce that flag on POST /contents, PUT_RELATIVE, LOCK, and other write operations.
• Include session-level write permission when returning WOPI FileInfo fields such as ReadOnly and UserCanWrite.

1. What is CVE-2026-62323? CVE-2026-62323 is a medium-severity incorrect authorization vulnerability in github.com/cloudreve/Cloudreve/v4 (go), affecting versions < 4.0.0-20260626022433-f3347130ac48. It is fixed in 4.0.0-20260626022433-f3347130ac48. The application does not correctly enforce access controls, allowing a principal to access resources or operations beyond their granted permissions.
2. How severe is CVE-2026-62323? CVE-2026-62323 has a CVSS score of 6.3 (Medium). This score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether it represents real risk in your environment depends on whether the vulnerable code is present and reachable.
3. Which packages are affected by CVE-2026-62323?
   • github.com/cloudreve/Cloudreve/v4 (go) (versions < 4.0.0-20260626022433-f3347130ac48)
   • github.com/cloudreve/Cloudreve/v3 (go) (versions <= 3.0.0-20250225100611-da4e44b77af4)
4. Is there a fix for CVE-2026-62323? Yes. CVE-2026-62323 is fixed in 4.0.0-20260626022433-f3347130ac48. Upgrade to this version or later.
5. Is CVE-2026-62323 exploitable, and should I be worried? Whether CVE-2026-62323 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
6. What actually determines whether CVE-2026-62323 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
7. How do I fix CVE-2026-62323? Upgrade github.com/cloudreve/Cloudreve/v4 to 4.0.0-20260626022433-f3347130ac48 or later.

Other vulnerabilities in github.com/cloudreve/Cloudreve/v4