CVE-2021-22879Public exploitNetwork attack vector

Command execution via unrestricted URL schemes

Published Apr 14, 2021 · Updated Aug 3, 2024

Resource injection in Nextcloud Desktop Client before 3.1.3 allows remote attackers controlling a server to execute commands after a user click. Server- and user-supplied URLs were passed to QDesktopServices::openUrl without restricting their schemes to HTTP or HTTPS, allowing registered local protocol handlers to launch commands. Exploitation requires the client to connect to a malicious server and a user to activate a crafted URL; successful execution runs with the user's privileges.

CVSS severity8.8
High
EPSS probability4.70%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Resource injection in Nextcloud Desktop Client before 3.1.3 allows remote attackers controlling a server to execute commands after a user click. Server- and user-supplied URLs were passed to QDesktopServices::openUrl without restricting their schemes to HTTP or HTTPS, allowing registered local protocol handlers to launch commands. Exploitation requires the client to connect to a malicious server and a user to activate a crafted URL; successful execution runs with the user's privileges.

The record

CVE
CVE-2021-22879
Published
Apr 14, 2021
Updated
Aug 3, 2024
Vendor
Nextcloud GmbH
Product
Nextcloud Desktop Client
Classifications
CWE-99, CWE-74, T1204.001
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Apr 14, 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 3.1.3

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Nextcloud GmbH · Nextcloud Desktop Clientversion=Fixed in 3.1.3

Published CVSS scores

6.8NIST NVDAV:N/AC:M/Au:N/C:P/I:P/A:P
8.8NIST NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/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 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 exploitPublished

Weakness, pattern, technique

CWE-99Improper Control of Resource Identifiers ('Resource Injection')
CWE-74Improper Neutralization of Special Elements in Output Used by a Downstream Component ('Injection')
T1204.001User Execution: Malicious Link

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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