CVE-2026-55499: Cloudreve: Broken access control in file event stream leaks activity events for unshared siblings to single-file share recipients

Severity: medium (CVSS 4.3 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.3% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2026-07-31 · updated 2026-09-08
Weakness: CWE-863

Description

Cloudreve is a self-hosted file management and sharing system. Prior to 4.17.0, a single-file share event-stream subscription resolves the share root to the owner’s parent folder and subscribes to that folder topic, allowing an authenticated share recipient to receive names, paths, rename targets, event types, and hashed identifiers for unshared sibling files and folders. This issue is fixed in version 4.17.0.

Affected products

cloudreve: before 4.17.0

References

https://github.com/cloudreve/cloudreve/commit/0b00dd308f132d6e6e8476857ef79f4865600bbc
https://github.com/cloudreve/cloudreve/releases/tag/4.17.0
https://github.com/cloudreve/cloudreve/security/advisories/GHSA-w8x7-h2px-xmq8
https://github.com/cloudreve/cloudreve/security/advisories/GHSA-w8x7-h2px-xmq8

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