CVE-2020-8121Network attack vector

Excess data exposure via improper reshare updates

Published Feb 4, 2020 · Updated Aug 4, 2024

Improper access control in Nextcloud Server 14.0.4 allows remote authenticated users to expose more data through reshared links. The share-update path fails to keep a reshared link's permissions within the access granted to the resharing account. A low-privileged account with resharing and link sharing available is required; the resulting link exposes content beyond the sharer's intended scope.

CVSS severity9.6
Critical
EPSS probability1.04%
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 14.0.4 allows remote authenticated users to expose more data through reshared links. The share-update path fails to keep a reshared link's permissions within the access granted to the resharing account. A low-privileged account with resharing and link sharing available is required; the resulting link exposes content beyond the sharer's intended scope.

The record

CVE
CVE-2020-8121
Published
Feb 4, 2020
Updated
Aug 4, 2024
Vendor
Nextcloud GmbH
Product
Nextcloud Server
Classifications
CWE-284, T1530
Attack vector
network
Privileges
authenticated

Timeline

How it unfolded

  1. Feb 4, 2020CVE publishedPublication date reported by the CVE source.
  2. Aug 4, 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=14.0.4

What conditions does exploitation require?

Attack vectornetwork
Required privilegesauthenticated

What is affected?

Nextcloud GmbH · Nextcloud Serverversion=14.0.4

Published CVSS scores

9.6Nextcloud GmbHCVSS:3.0/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:N
8.1NIST NVDCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:N
5.5NIST NVDAV:N/AC:L/Au:S/C:P/I:P/A:N

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.

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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 - Generic
T1530Data from Cloud Storage

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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