CVE-2021-22895Network attack vector

Provider registration manipulation via accepted invalid certificates

Published Jun 11, 2021 · Updated Aug 3, 2024

Improper certificate validation in Nextcloud Desktop Client before 3.3.1 allows man-in-the-middle attackers to alter provider-registration traffic. WebEnginePage::certificateError returned success for CertificateAuthorityInvalid when the certificate host matched the registration page's root host, causing QWebEngine to continue despite an untrusted issuer. Exploitation requires a network interception position during the Register with a Provider flow and permits modification of that registration session.

CVSS severity5.9
Medium
EPSS probability1.03%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
Coverage for this vulnerability

See if you're affected

Explore vulnerability checks for your environment with Hinoki.

Book a demo

Summary

What happened

Improper certificate validation in Nextcloud Desktop Client before 3.3.1 allows man-in-the-middle attackers to alter provider-registration traffic. WebEnginePage::certificateError returned success for CertificateAuthorityInvalid when the certificate host matched the registration page's root host, causing QWebEngine to continue despite an untrusted issuer. Exploitation requires a network interception position during the Register with a Provider flow and permits modification of that registration session.

The record

CVE
CVE-2021-22895
Published
Jun 11, 2021
Updated
Aug 3, 2024
Vendor
Nextcloud GmbH
Product
Nextcloud Desktop Client
Classifications
CWE-295, T1557
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Jun 11, 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

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=Fixed in 3.3.1

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Nextcloud GmbH · Nextcloud Desktop Clientversion=Fixed in 3.3.1

Published CVSS scores

4.3NIST NVDAV:N/AC:M/Au:N/C:N/I:P/A:N
5.9NIST NVDCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/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.

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
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-295Improper Certificate Validation
T1557Adversary-in-the-Middle

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

See the directory against your own environment.

Your stack

Check the software in your environment

Book a demo to see how Hinoki identifies affected software and validates exploitability in your environment.

Book a demo