High 7.1Published Sep 22, 2026

CVE-2026-77633Cloudreve: Storage-quota TOCTOU race allows quota bypass and storage-based denial of service

Updated under an hour ago (2026-10-19 10:20 UTC)

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Exploited in the last 30 days

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: 7.1 HIGH (v3.1, CNA)CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:L/A:H
Weakness (CWE): CWE-362, CWE-367, CWE-770
Known exploited: Not in CISA's KEV catalog
EPSS (exploitation in the next 30 days): Not loaded for this CVE
Assigned by: GitHub_M
NVD analysis: Deferred
Record last updated: Sep 25, 2026
First seen by InfoSec Signals: Oct 9, 2026

Affected products

Affected products

cloudreve cloudreve cloudreve:cloudreve (from the name)	before 4.18.0	CNA record

References

https://github.com/cloudreve/cloudreve/security/advisories/GHSA-xj3h-wwxq-gfcjx-refsource-confirm
https://github.com/cloudreve/cloudreve/commit/7329602751c00bb4136fe9ad8b364d0df70773dfx-refsource-misc
https://github.com/cloudreve/cloudreve/releases/tag/4.18.0x-refsource-misc

The CVE record on cve.org NVD's entry

The CVE record is authoritative. Products marked “from the name” were identified from the CNA's free-text names, not a CPE, and are matched less certainly. This product uses the NVD API but is not endorsed or certified by the NVD.