CVE-2021-22877Public exploitNetwork attack vector

Cross-user credential assignment via missing session check

Published Mar 3, 2021 · Updated Aug 3, 2024

Missing authorization in Nextcloud Server before 20.0.6 allows remote authenticated users to misassign external-storage credentials. LoginCredentials::getCredentials uses credentials from the current session for a requested user without verifying that both user identifiers match. An administrator must load the user list on a deployment using stored external-storage credentials; uninitialized user rows can then receive the administrator's credentials, causing cross-user access or failed mounts.

CVSS severity6.5
Medium
EPSS probability1.69%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Missing authorization in Nextcloud Server before 20.0.6 allows remote authenticated users to misassign external-storage credentials. LoginCredentials::getCredentials uses credentials from the current session for a requested user without verifying that both user identifiers match. An administrator must load the user list on a deployment using stored external-storage credentials; uninitialized user rows can then receive the administrator's credentials, causing cross-user access or failed mounts.

The record

CVE
CVE-2021-22877
Published
Mar 3, 2021
Updated
Aug 3, 2024
Vendor
Nextcloud GmbH
Product
Nextcloud Server
Classifications
CWE-862, CWE-284
Attack vector
network
Privileges
admin

Timeline

How it unfolded

  1. Mar 3, 2021CVE publishedPublication date reported by the CVE source.
  2. Aug 3, 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=Fixed in 20.0.6

What conditions does exploitation require?

Attack vectornetwork
Required privilegesadmin

What is affected?

Nextcloud GmbH · Nextcloud Serverversion=Fixed in 20.0.6

Published CVSS scores

5.5NIST NVDAV:N/AC:L/Au:S/C:P/I:P/A:N
6.5NIST NVDCVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:H/I:H/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
Privilegesadmin
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

CWE-862Missing Authorization
CWE-284Improper Access Control

Public exploit references

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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