CVE-2021-21320

What it is

matrix-react-sdk is an npm package which is a Matrix SDK for React Javascript. In matrix-react-sdk before version 3.15.0, the user content sandbox can be abused to trick users into opening unexpected documents. The content is opened with a `blob` origin that cannot access Matrix user data, so messages and secrets are not at risk. This has been fixed in version 3.15.0.

At a glance

Exploitability

Can be exploited over the network with a low-privilege account, but needs a user to act. Limited direct impact.

Exploit odds

0.9% chance of exploitation in the next 30 days (EPSS).

Fix

A patch, advisory or fixed version is referenced. Upgrade or apply it.

Timeline

1. 2021-03-02 03:15 UTC PublishedDisclosed publicly on CVE.org and NVD
2. 2026-06-17 03:35 UTC Last updatedMost recent change to the record

Why it ranks here

• Exploited in the wild: no, CISA does not list it.
• Exploit odds: 0.9% in the next 30 days (EPSS).
• Severity: 2.6 LOW (CVSS).
• Fix: a patch or advisory is linked.

Details

Published

2021-03-02 03:15 UTC

Last modified

2026-06-17 03:35 UTC

Exploit probability

0.9% · EPSS, next 30 days

Weakness

CWE-345

Record status

Modified

Affected

• matrix-react-sdk Project matrix-react-sdk < 3.15.0

Attack profile CVSS 3.1 · 2.6

Attack vector

Network

Complexity

High

Privileges needed

Low

User interaction

Required

Scope

Unchanged

Confidentiality

None

Integrity

Low

Availability

None

Is it in your code?

Hand this to your coding agent. It searches your project for the affected products and checks versions. Nothing leaves your machine.

Read https://cve-list.com/agent/cve/CVE-2021-21320.md and follow it. Check whether this project is affected by CVE-2021-21320. Read only. Don't change anything and don't upload my code. Tell me yes, no or not sure, with the file as proof.

Copy as ticket · More options · Status badge