CVE-2023-48239Network attack vector

Shared-storage denial via missing ownership check

Published Nov 21, 2023 · Updated Jun 10, 2025

Improper access control in Nextcloud Server allows remote authenticated users to make shared external storage inaccessible. UserStoragesService::updateStorage trusted a caller-supplied storage ID and updated it without first invoking getStorage to enforce ownership and applicability. Any account with the files_external app enabled can alter personal or global mount configurations and deny storage access to other users.

CVSS severity8.5
High
EPSS probability0.95%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Improper access control in Nextcloud Server allows remote authenticated users to make shared external storage inaccessible. UserStoragesService::updateStorage trusted a caller-supplied storage ID and updated it without first invoking getStorage to enforce ownership and applicability. Any account with the files_external app enabled can alter personal or global mount configurations and deny storage access to other users.

The record

CVE
CVE-2023-48239
Published
Nov 21, 2023
Updated
Jun 10, 2025
Vendor
Nextcloud GmbH
Product
Security Advisories
Classifications
CWE-284, T1565.001
Attack vector
network
Privileges
authenticated

Timeline

How it unfolded

  1. Nov 21, 2023CVE publishedPublication date reported by the CVE source.
  2. Jun 10, 2025Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

Compare your product and version with the public record. A matching version still requires validation against your environment.

Is a vulnerable build present?

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

  1. Affected versionversion=>= 20.0.0, < 20.0.14.16
  2. Affected versionversion=>= 21.0.0, < 21.0.9.13
  3. Affected versionversion=>= 22.0.0, < 22.2.10.15
  4. Affected versionversion=>= 23.0.0, < 23.0.12.12
  5. Affected versionversion=>= 24.0.0, < 24.0.12.8
  6. Affected versionversion=>= 25.0.0, < 25.0.13
  7. Affected versionversion=>= 26.0.0, < 26.0.8
  8. Affected versionversion=>= 27.0.0, < 27.1.3

What conditions does exploitation require?

Attack vectornetwork
Required privilegesauthenticated

What is affected?

Nextcloud GmbH · Security Advisoriesversion=>= 20.0.0, < 20.0.14.16; version=>= 21.0.0, < 21.0.9.13; version=>= 22.0.0, < 22.2.10.15; version=>= 23.0.0, < 23.0.12.12; version=>= 24.0.0, < 24.0.12.8; version=>= 25.0.0, < 25.0.13; version=>= 26.0.0, < 26.0.8; version=>= 27.0.0, < 27.1.3

Published CVSS scores

8.5GitHubCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:N/I:L/A:H
7.1INCIBE-CERTCVSS: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.

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

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-284Improper Access Control
T1565.001Data Manipulation: Stored Data Manipulation

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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