CVE-2021-32726Network attack vector

Account takeover via orphaned WebAuthn credentials

Published Jul 12, 2021 · Updated Aug 3, 2024

Authentication bypass in Nextcloud Server allows remote authenticated users with retained WebAuthn credentials to access reused accounts. Before 19.0.13, 20.0.0 through 20.0.10, and 21.0.0 through 21.0.2, the user-deletion path lacked a deletion-event listener for the WebAuthn table, leaving the former user's credential associated with the deleted username. Exploitation requires account deletion, reuse of its username, and possession of the former user's registered authenticator; access is limited to the replacement account.

CVSS severity7.1
High
EPSS probability1.78%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Authentication bypass in Nextcloud Server allows remote authenticated users with retained WebAuthn credentials to access reused accounts. Before 19.0.13, 20.0.0 through 20.0.10, and 21.0.0 through 21.0.2, the user-deletion path lacked a deletion-event listener for the WebAuthn table, leaving the former user's credential associated with the deleted username. Exploitation requires account deletion, reuse of its username, and possession of the former user's registered authenticator; access is limited to the replacement account.

The record

CVE
CVE-2021-32726
Published
Jul 12, 2021
Updated
Aug 3, 2024
Vendor
Nextcloud GmbH
Product
Nextcloud Security Advisories
Classifications
CWE-708, CWE-287, T1078
Attack vector
network
Privileges
authenticated

Timeline

How it unfolded

  1. Jul 12, 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=< 19.0.13
  2. Affected versionversion=>= 20.0.0, < 20.0.11
  3. Affected versionversion=>= 21.0.0, < 21.0.3

What conditions does exploitation require?

Attack vectornetwork
Required privilegesauthenticated

What is affected?

Nextcloud GmbH · Nextcloud Security Advisoriesversion=< 19.0.13; version=>= 20.0.0, < 20.0.11; version=>= 21.0.0, < 21.0.3

Published CVSS scores

7.1GitHub, Inc.CVSS:3.1/AV:N/AC:H/PR:L/UI:R/S:U/C:H/I:H/A:H
9.8NIST National Vulnerability DatabaseCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
7.5NIST National Vulnerability DatabaseAV:N/AC:L/Au:N/C:P/I:P/A:P

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-708Incorrect Ownership Assignment
CWE-287Improper Authentication
T1078Valid Accounts

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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