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Vulnerability record · CVE-2026-77633 · published 22 September 2026

CVE-2026-77633: Race condition vulnerability

Cloudreve is a self-hosted file management and sharing system. Prior to 4.18.0, PrepareUpload in pkg/filemanager/fs/dbfs/upload.go checks a stale in-memory user storage value through validateUserCapacity and later applies an unconditional storage charge outside the same quota-enforcing transaction. An authenticated user with Files.Write permission can issue concurrent upload-session requests that read the same capacity snapshot, all pass the MaxStorage check, and reserve their declared sizes through CommitWithStorageDiff. The resulting reservations can exceed the account quota and can be materialized as chunked uploads that exhaust host storage and deny uploads to other users. The default local-storage policy and default User group are affected. This issue is fixed in version 4.18.0.

7.1 CVSS 3.1 High EPSS 0.37% · top 71.8% CWE-362 · Race conditionCWE-367 · TOCTOU race condition Deferred
7.1CVSS 3.1 base score
0.37%EPSS exploitation probability, 30 days
NoNot in CISA KEV
0Affected product versions listed by NVD
3References
26 Sep 2026Last modified by NVD

Description

Cloudreve is a self-hosted file management and sharing system. Prior to 4.18.0, PrepareUpload in pkg/filemanager/fs/dbfs/upload.go checks a stale in-memory user storage value through validateUserCapacity and later applies an unconditional storage charge outside the same quota-enforcing transaction. An authenticated user with Files.Write permission can issue concurrent upload-session requests that read the same capacity snapshot, all pass the MaxStorage check, and reserve their declared sizes through CommitWithStorageDiff. The resulting reservations can exceed the account quota and can be materialized as chunked uploads that exhaust host storage and deny uploads to other users. The default local-storage policy and default User group are affected. This issue is fixed in version 4.18.0.

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

References

LinkTags
https://github.com/cloudreve/cloudreve/commit/7329602751c00bb4136fe9ad8b364d0df70773df
https://github.com/cloudreve/cloudreve/releases/tag/4.18.0
https://github.com/cloudreve/cloudreve/security/advisories/GHSA-xj3h-wwxq-gfcj

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Source: NIST National Vulnerability Database (record CVE-2026-77633), CISA KEV, FIRST EPSS (scores of 2026-09-27). This page is refreshed as NVD updates the record.