CVE-2021-32622

Local script execution via unsafe preview MIME type

Published May 17, 2021 · Updated Aug 3, 2024

Cross-site scripting in Matrix.org matrix-react-sdk before 3.21.0 allows local users to run scripts through an uploaded file preview. The upload confirmation preview preserved script-capable MIME types instead of replacing unsafe types before displaying the local blob. Exploitation requires several user actions and opening the preview in a separate tab; other users and remote attackers cannot trigger it.

CVSS severity4.2
Medium
EPSS probability0.37%
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

Cross-site scripting in Matrix.org matrix-react-sdk before 3.21.0 allows local users to run scripts through an uploaded file preview. The upload confirmation preview preserved script-capable MIME types instead of replacing unsafe types before displaying the local blob. Exploitation requires several user actions and opening the preview in a separate tab; other users and remote attackers cannot trigger it.

The record

CVE
CVE-2021-32622
Published
May 17, 2021
Updated
Aug 3, 2024
Vendor
Matrix.org
Product
matrix-react-sdk
Classifications
CWE-74, CWE-434
Attack vector
local
Privileges
authenticated

Timeline

How it unfolded

  1. May 17, 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=< 3.21.0

What conditions does exploitation require?

Attack vectorlocal
Required privilegesauthenticated

What is affected?

Matrix.org · matrix-react-sdkversion=< 3.21.0

Published CVSS scores

7.8NIST NVDCVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H
4.2GitHub, Inc.CVSS:3.1/AV:L/AC:H/PR:L/UI:R/S:U/C:L/I:L/A:L
4.4NIST NVDAV:L/AC:M/Au:N/C:P/I:P/A:P

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)
Vectorlocal
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-74Improper Neutralization of Special Elements in Output Used by a Downstream Component ('Injection')
CWE-434Unrestricted Upload of File with Dangerous Type

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