Is CVE-2021-21332 in the CISA KEV catalog?

No. CVE-2021-21332 is not currently on the CISA Known Exploited Vulnerabilities list.

What is the CVSS severity of CVE-2021-21332?

CVE-2021-21332 has a CVSS v3 base score of 6.9 (MEDIUM).

What is the EPSS score for CVE-2021-21332?

CVE-2021-21332 has an EPSS score of 1.22% (65th percentile), estimating the probability of exploitation in the next 30 days.

How do I fix CVE-2021-21332?

Upgrade matrix-synapse on debian unstable to 1.27.0-1 or later.

CVE & CISA-KEV Catalog

CVE-2021-21332

MEDIUM

6.9

CVSS v3

NVD

Description

Synapse is a Matrix reference homeserver written in python (pypi package matrix-synapse). Matrix is an ecosystem for open federated Instant Messaging and VoIP. In Synapse before version 1.27.0, the password reset endpoint served via Synapse was vulnerable to cross-site scripting (XSS) attacks. The impact depends on the configuration of the domain that Synapse is deployed on, but may allow access to cookies and other browser data, CSRF vulnerabilities, and access to other resources served on the same domain or parent domains. This is fixed in version 1.27.0.

CWE-79Cross-Site Scripting (XSS)

How to fix

Remediation Available

matrix-synapseDebian

Fixed in:1.27.0-1CVE-2021-21332

Remediation is compiled from vendor and distribution security advisories. Always confirm against the linked source for your exact version and platform.

CVSS v3 Vector

Exploitability

Attack VectorNetwork

Attack ComplexityHigh

Privileges RequiredNone

User InteractionRequired

ScopeChanged

Impact

ConfidentialityHigh

IntegrityLow

AvailabilityNone

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

Exploit Intelligence

1.22%probability of exploitation in 30 days

65thpercentile

Moderate risk: more likely to be exploited than 65% of all known CVEs.

References

Patch2

Third-Party Advisory2

Other references1

lists.fedoraproject.org

Related Vulnerabilities

Other CWE-79 (Cross-Site Scripting (XSS)) vulnerabilities, ordered by exploit likelihood. View all

CVE	Severity	CVSS	EPSS	Exploited	Fix
CVE-2020-11022	Medium	6.9	99%	-	Fix
CVE-2019-3929	Critical	9.8	99%	KEV	Fix
CVE-2020-9496	Medium	6.1	99%	-	-
CVE-2023-28341	Medium	6.1	99%	-	Fix
CVE-2018-12998	Medium	6.1	98%	-	-
CVE-2025-4123	High	7.6	98%	-	Fix

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This product uses NVD data but is not endorsed or certified by the NVD. EPSS scores courtesy of FIRST.org (https://www.first.org/epss). Source: CISA KEV Catalog. Data as of 2024-11-21.