CVE-2026-77633Network attack vectorHinoki check available

Storage exhaustion via non-atomic quota reservation

Published Sep 22, 2026 · Updated Sep 22, 2026

A quota race in Cloudreve 4.17.0 and earlier allows remote authenticated users to exceed storage limits and exhaust host storage. PrepareUpload checks a stale in-memory storage snapshot, then CommitWithStorageDiff unconditionally charges each concurrent reservation outside the quota-enforcing transaction. Files.Write permission in the default User group and local-storage policy is sufficient; completed chunked uploads can fill the disk and deny uploads to other users.

CVSS severity7.1
High
EPSS probability0.37%
Next 30 days · Oct 19, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
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Summary

What happened

A quota race in Cloudreve 4.17.0 and earlier allows remote authenticated users to exceed storage limits and exhaust host storage. PrepareUpload checks a stale in-memory storage snapshot, then CommitWithStorageDiff unconditionally charges each concurrent reservation outside the quota-enforcing transaction. Files.Write permission in the default User group and local-storage policy is sufficient; completed chunked uploads can fill the disk and deny uploads to other users.

The record

CVE
CVE-2026-77633
Published
Sep 22, 2026
Updated
Sep 22, 2026
Vendor
Cloudreve
Product
Cloudreve
Classifications
CWE-367, CWE-770, CWE-362, T1499.004
Attack vector
network
Privileges
authenticated

Timeline

How it unfolded

  1. Sep 22, 2026CVE publishedPublication date reported by the CVE source.
  2. Sep 22, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=< 4.18.0

What conditions does exploitation require?

Attack vectornetwork
Required privilegesauthenticated

What is affected?

Cloudreve · Cloudreveversion=< 4.18.0

Published CVSS scores

7.1GitHubCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:L/A:H

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Activity data is delayed. The latest report is Sep 28, 2026.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 22, 2026Sep 28, 2026
Latest reporting daySep 28, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-367Time-of-check Time-of-use (TOCTOU) Race Condition
CWE-770Allocation of Resources Without Limits or Throttling
CWE-362Concurrent Execution using Shared Resource with Improper Synchronization ('Race Condition')
T1499.004Application or System Exploitation

Public exploit references

No public exploit references are available in this record.

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Technologies

Your stack

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Your stack

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