CVE-2021-32733Network attack vector

Cross-site scripting via incorrect content type

Published Jul 12, 2021 · Updated Aug 3, 2024

Nextcloud Text before 19.0.13, 20.0.11, and 21.0.3 allows remote authenticated users to inject script through served documents. The application fetched document files with a text/html Content-Type, causing browser HTML interpretation instead of text rendering. Exploitation requires a user to open crafted content; modern browsers enforcing the shipped Content-Security-Policy block script execution, limiting impact to browsers without that protection.

CVSS severity6.1
Medium
EPSS probability1.11%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Nextcloud Text before 19.0.13, 20.0.11, and 21.0.3 allows remote authenticated users to inject script through served documents. The application fetched document files with a text/html Content-Type, causing browser HTML interpretation instead of text rendering. Exploitation requires a user to open crafted content; modern browsers enforcing the shipped Content-Security-Policy block script execution, limiting impact to browsers without that protection.

The record

CVE
CVE-2021-32733
Published
Jul 12, 2021
Updated
Aug 3, 2024
Vendor
Nextcloud GmbH
Product
Nextcloud Security Advisories
Classifications
CWE-79, T1189
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

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=< 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

6.1NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N
4.3NVDAV:N/AC:M/Au:N/C:N/I:P/A:N
4.8GitHub, Inc.CVSS:3.1/AV:N/AC:H/PR:L/UI:R/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 9, 2026Sep 15, 2026
Latest reporting daySep 15, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

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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