CVE-2026-77637: Auth Bypass (CVSS 3.8)

Description

Cloudreve is a self-hosted file management and sharing system. Prior to 4.18.0, tool.GET("wopi") and tool.POST("mail") in routers/router.go inherit ScopeAdminRead but omit the RequiredScopes(types.ScopeAdminWrite) middleware applied to neighboring state-changing admin tool routes. An OAuth application or API key limited to Admin.Read can therefore probe configured WOPI service endpoints and send arbitrary test email through the server SMTP configuration, exceeding the token's intended read-only authorization boundary. This issue is fixed in version 4.18.0.

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CVSS v3.1 Score

3.8

LOW

CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:L/I:L/A:N

EPSS — Exploit Prediction

0.0033

Probability of exploitation

0.24%

Percentile rank

EPSS estimates the probability that this vulnerability will be exploited in the wild within the next 30 days. A higher score means more likely to be exploited.

Weakness Type (CWE)

CWE-862 Missing Authorization

References

Other References

https://github.com/cloudreve/cloudreve/commit/bce08f88e9d8f881e78fd18e7a6598b31922c492 https://github.com/cloudreve/cloudreve/releases/tag/4.18.0 https://github.com/cloudreve/cloudreve/security/advisories/GHSA-w89x-c962-c44g

Frequently Asked Questions

What is CVE-2026-77637? +

Cloudreve is a self-hosted file management and sharing system. Prior to 4.18.0, tool.GET("wopi") and tool.POST("mail") in routers/router.go inherit ScopeAdminRead but omit the RequiredScopes(types.ScopeAdminWrite) middleware applied to neighboring state-changing admin tool routes. An OAuth application or API key limited to Admin.Read can therefore probe configured WOPI service endpoints and send arbitrary test email through the server SMTP configuration, exceeding the token's intended read-only authorization boundary. This issue is fixed in version 4.18.0. It has a CVSS v3.1 base score of 3.8 (LOW).

How severe is CVE-2026-77637? +

CVE-2026-77637 has a CVSS v3.1 score of 3.8 out of 10, rated LOW. This is a low-severity vulnerability with limited impact. The EPSS score is 0.0033, placing it in the 0th percentile for exploitation probability.

How do I check if I'm vulnerable to CVE-2026-77637? +

You can use Secably's free Website Scanner to check your website for known vulnerabilities. For infrastructure scanning, use the Port Scanner to identify exposed services that may be affected. Check the vendor advisories linked above for specific patch and version information.

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