CVE-2021-21332

Cross-site scripting (XSS) vulnerability in the password reset endpoint

HIGH
8.2
CVSS Score
Published: March 26, 2021 at 07:55 PM UTC
Updated: June 17, 2026 at 03:35 AM UTC
3 products affected across 3 vendorsFedoraSynapseSynapse

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Severity
HIGH8.2
Exploit prediction
EPSS 1%

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.

Affected

Our own answer: ranges merged, affected separated from platform-only, with confidence and review flags.

v < 1.27.0
Affected range stops below 1.27.0, so it looks safe — our inference, not a vendor statement
v < 1.27.0
Affected range stops below 1.27.0, so it looks safe — our inference, not a vendor statement

CVSS

Attack Vector
NETWORK
Complexity
LOW
Privileges
NONE
User Interaction
REQUIRED
Scope
CHANGED
Confidentiality
HIGH
Integrity
LOW
Availability
NONE
Vector?

Quick Info

StatusMODIFIED
CWE
CWE-79

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