CVE-2021-39222Network attack vector

Stored XSS via malicious file tab

Published Nov 15, 2021 · Updated Aug 4, 2024

Cross-site scripting in Nextcloud Talk before 10.0.7, 10.1.4, 11.1.2, 11.2.0, or 12.0.0 allows remote attackers to execute script in a user's browser. The stored payload is reached when a user right-clicks a malicious file and opens it in a new tab, causing the Talk file view to render attacker-controlled content. Exploitation requires that user interaction and a browser without effective Content-Security-Policy; modern browsers enforcing the shipped policy block script execution.

CVSS severity6.1
Medium
EPSS probability1.10%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Cross-site scripting in Nextcloud Talk before 10.0.7, 10.1.4, 11.1.2, 11.2.0, or 12.0.0 allows remote attackers to execute script in a user's browser. The stored payload is reached when a user right-clicks a malicious file and opens it in a new tab, causing the Talk file view to render attacker-controlled content. Exploitation requires that user interaction and a browser without effective Content-Security-Policy; modern browsers enforcing the shipped policy block script execution.

The record

CVE
CVE-2021-39222
Published
Nov 15, 2021
Updated
Aug 4, 2024
Vendor
Nextcloud GmbH
Product
Nextcloud Security Advisories
Classifications
CWE-434, CWE-79, T1189
Attack vector
network
Privileges
authenticated

Timeline

How it unfolded

  1. Nov 15, 2021CVE 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

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=< 10.0.7
  2. Affected versionversion=>= 10.1.0, < 10.1.4
  3. Affected versionversion=>= 11.1.0, < 11.1.2
  4. Affected versionversion=< 11.2.0
  5. Affected versionversion=>= 12.0.0.alpha-1, < 12.0.0

What conditions does exploitation require?

Attack vectornetwork
Required privilegesauthenticated

What is affected?

Nextcloud GmbH · Nextcloud Security Advisoriesversion=< 10.0.7; version=>= 10.1.0, < 10.1.4; version=>= 11.1.0, < 11.1.2; version=< 11.2.0; version=>= 12.0.0.alpha-1, < 12.0.0

Published CVSS scores

4.3NVDAV:N/AC:M/Au:N/C:N/I:P/A:N
6.1NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/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
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-434Unrestricted Upload of File with Dangerous Type
CWE-79Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')
T1189Drive-by Compromise

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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