Vulnerability · Published Sep 22, 2026 · Assigned by GitHub_M
CVE-2026-77633Cloudreve: Storage-quota TOCTOU race allows quota bypass and storage-based denial of service
High 7.1
In plain English
A high-severity race condition in cloudreve from cloudreve. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.4% (higher than 31% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.
Official 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.
Affected packages & fixed versions
| Ecosystem | Package | Fixed in | Advisory |
|---|---|---|---|
| Go | github.com/cloudreve/Cloudreve | no fix listed | GO-2026-6578 |
| Go | github.com/cloudreve/Cloudreve/v3 | no fix listed | GO-2026-6578 |
| Go | github.com/cloudreve/Cloudreve/v4 | 4.0.0-20260715025621-7329602751c0 | GHSA-xj3h-wwxq-gfcj |
| Go | github.com/cloudreve/Cloudreve/v4 | 4.0.0-20260715025621-7329602751c0 | GO-2026-6578 |
Affected products (as reported)
Weakness: CWE-362, CWE-367, CWE-770 · Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:L/A:H