CVE-2021-32679Network attack vector

Executable download spoofing via unescaped Content-Disposition filenames

Published Jul 12, 2021 · Updated Aug 3, 2024

Improper output escaping in Nextcloud Server before 19.0.13, 20.0.11, or 21.0.3 allows remote authenticated users to spoof downloads. DownloadResponse inserted user-supplied filenames into the Content-Disposition header without escaping apostrophes and backslashes, allowing a displayed benign extension to differ from the downloaded executable extension. Exploitation requires an application to pass an attacker-controlled filename and a user to initiate the download; the reported consequence is download deception, not server code execution.

CVSS severity3.5
Low
EPSS probability1.37%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Improper output escaping in Nextcloud Server before 19.0.13, 20.0.11, or 21.0.3 allows remote authenticated users to spoof downloads. DownloadResponse inserted user-supplied filenames into the Content-Disposition header without escaping apostrophes and backslashes, allowing a displayed benign extension to differ from the downloaded executable extension. Exploitation requires an application to pass an attacker-controlled filename and a user to initiate the download; the reported consequence is download deception, not server code execution.

The record

CVE
CVE-2021-32679
Published
Jul 12, 2021
Updated
Aug 3, 2024
Vendor
Nextcloud GmbH
Product
Nextcloud Security Advisories
Classifications
CWE-116, T1204.002
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

8.8NIST NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H
6.8NIST NVDAV:N/AC:M/Au:N/C:P/I:P/A:P
3.5GitHub, Inc.CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:U/C:N/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-116Improper Encoding or Escaping of Output
T1204.002User Execution: Malicious File

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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