CVE-2019-15621Network attack vector

Data modification via writable public-link reshare

Published Feb 4, 2020 · Updated Aug 5, 2024

Improper permission preservation in Nextcloud Server 16.0.1 allows remote authenticated users to create writable public links. The public-link reshare path fails to preserve a received share's restrictions when its mount point is shared, assigning write permission to the new link. A user who can reshare a received mount-point share can expose its contents to modification by anyone holding the resulting public link.

CVSS severity6.4
Medium
EPSS probability1.06%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Improper permission preservation in Nextcloud Server 16.0.1 allows remote authenticated users to create writable public links. The public-link reshare path fails to preserve a received share's restrictions when its mount point is shared, assigning write permission to the new link. A user who can reshare a received mount-point share can expose its contents to modification by anyone holding the resulting public link.

The record

CVE
CVE-2019-15621
Published
Feb 4, 2020
Updated
Aug 5, 2024
Vendor
Nextcloud GmbH
Product
Nextcloud Server
Classifications
CWE-281, T1565.001
Attack vector
network
Privileges
authenticated

Timeline

How it unfolded

  1. Feb 4, 2020CVE publishedPublication date reported by the CVE source.
  2. Aug 5, 2024Record 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=16.0.2

What conditions does exploitation require?

Attack vectornetwork
Required privilegesauthenticated

What is affected?

Nextcloud GmbH · Nextcloud Serverversion=16.0.2

Published CVSS scores

4.0NIST NVDAV:N/AC:L/Au:S/C:N/I:P/A:N
6.5NIST NVDCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:H/A:N
6.4NextcloudCVSS:3.0/AV:N/AC:H/PR:L/UI:R/S:U/C:N/I:H/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 9, 2026Sep 15, 2026
Latest reporting daySep 15, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-281Improper Preservation of Permissions
T1565.001Stored Data Manipulation

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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