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CVE-2021-21320

17
FAUCET Score

CVE-2021-21320 affects matrix-react-sdk versions prior to 3.15.0, allowing an attacker to trick users into opening unexpected documents through a user content sandbox bypass. The vulnerability has a CVSS score of 4.3 (Medium) due to its reliance on user interaction (UI:R) and low impact (I:L), as it cannot access sensitive Matrix user data. There is currently no evidence of active exploitation, public exploit code, or significant community discussion surrounding this vulnerability.

Impacted Technologies

VendorProductVersion(s)CPE
< 3.15.0CPE matchmatch criteria
cpe:2.3:a:matrix-react-sdk_project:matrix-react-sdk:*:*:*:*:*:node.js:*:*

CVSS Data

CVSS version used by this source: 3.1

2.6LOW

CVSS:3.1/AV:N/AC:H/PR:L/UI:R/S:U/C:N/I:L/A:N

Attack Vector
NETWORK
Attack Complexity
HIGH
Privileges Required
LOW
User Interaction
REQUIRED
Scope
UNCHANGED
Confidentiality Impact
NONE
Integrity Impact
LOW
Availability Impact
NONE
Exploitability Score
1.2
Impact Score
1.4
CvssVersion
3.1

Exploit Intelligence

EPSS Score
0.92%
Probability of exploitation in next 30 days
EPSS Percentile
56.7%
Percentile rank of EPSS score among Peer Group
As of 2026-07-27
Model: v2026.06.15
This CVE's current EPSS score of 0.0092 is in the 68th percentile among its peer group of 26,221 CVEs.

Social Chatter

The average CVE in this peer group has 0.0 Twitter, 0.0 Reddit, 0.1 Bluesky, 0.0 Mastodon, and 0.1 GitHub mentions.

Media Mentions

No media coverage found for this CVE.

The average CVE in this peer group has 0.1 InfoSec Media, 0.0 Vendor Blog, and 0.0 Security Researcher mentions.

Remediation

Patch Available

Vendor Patches (2)

github_advisorypatch availablevia nvd_reference
View patch
npmpatch availablevia ghsa
Product: matrix-react-sdkFixed in: 3.15.0

Vendor Advisories (1)

npmGHSA-52mq-6jcv-j79xlow

User content sandbox can be confused into opening arbitrary documents

Mar 3, 2021

References

github.com / matrix-org/matrix-react-sdk/commit/b386f0c73b95ecbb6ea7f8f79c6ff5171a8dedd1
PatchThird Party Advisory
github.com / matrix-org/matrix-react-sdk/pull/5657
PatchThird Party Advisory
github.com / matrix-org/matrix-react-sdk/security/advisories/GHSA-52mq-6jcv-j79x
Third Party Advisory
npmjs.com / package/matrix-react-sdk
ProductThird Party Advisory