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Fencer Vulns
high 7.1

CVE-2026-77633 json

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

published 2026-09-22 47 d ago modified 2026-10-01 38 d ago also GHSA-xj3h-wwxq-gfcj , GO-2026-6578 , EUVD-2026-84528

cvss
7.1
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
0.4%
EPSS 0.4% chance of exploitation in 30 days, percentile 30%
public exploits
0
none known

Summary

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.

Patch / fix

  • go github.com/cloudreve/Cloudreve/v4 4.0.0-20260715025621-7329602751c0

CISA SSVC

Exploitation
none
Automatable
no
Technical impact
partial
Assessed
44 d ago

Exploit prediction

0.37% chance of exploitation in the next 30 days, higher than 30% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by version score vector
CNA 3.1 7.1 CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:L/A:H
GitHub 3.1 7.1 CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:L/A:H

Affected packages

ecosystem package affected fixed in
go github.com/cloudreve/Cloudreve/v4
<4.0.0-20260715025621-7329602751c0
4.0.0-20260715025621-7329602751c0
go github.com/cloudreve/Cloudreve
all versions
 no fix listed
go github.com/cloudreve/Cloudreve/v3
all versions
 no fix listed

Affected products

  • cloudreve cloudreve

Classification

Weakness
  • CWE-362 Concurrent Execution using Shared Resource with Improper Synchronization
  • CWE-367 Time-of-check Time-of-use (TOCTOU) Race Condition
  • CWE-770 Allocation of Resources Without Limits or Throttling

References

Sources

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.