Synapse
CVE-2021-21332
HIGH
Vulnerability Assessment
| Weakness |
CWE
OWASP Top 10:2025
A05:2025 - Injection
ASVS 5.0
V1 - Encoding and Sanitization Output encoding, context-aware escaping
MITRE ATT&CK
2 techniques across 2 tactics: Initial Access, Execution The technique list with ATT&CK links and the kill-chain view is part of the Basic plan and up. |
| Impact | CVSS score of 8.2 (HIGH). Attack characteristics: network attack vector, low complexity, no privileges required, user interaction required. |
| Exploit ScenarioDerived | A remote attacker could inject malicious scripts into web pages viewed by other users by sending crafted requests to the affected application. No authentication is required to exploit this vulnerability. |
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Alert meAnalysisAI
Synapse is a Matrix reference homeserver written in python (pypi package matrix-synapse). Rated high severity (CVSS 8.2), this vulnerability is remotely exploitable, no authentication required, low attack complexity. This Cross-Site Scripting (XSS) vulnerability could allow attackers to inject malicious scripts into web pages viewed by other users.
RemediationAI
A vendor patch is available. Apply the latest security update as soon as possible. Sanitize all user input, use Content-Security-Policy headers, encode output contextually (HTML, JS, URL). Use frameworks with built-in XSS protection.
Affected Packages
Source: OSV (Open Source Vulnerabilities)
Affects your stack
Affects 1 package in pypi
Checking this CVE against your own stacks and servers is part of the Basic plan and up.
Technical ContextAI · show details
This vulnerability is classified as Cross-Site Scripting (XSS) (CWE-79), which allows attackers to inject malicious scripts into web pages viewed by other users. 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 products include: Matrix Synapse, Fedoraproject Fedora. Version information: version 1.27.0.
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- Exploit and PoC references, threat intelligence from 22 sources
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Severity by source
AV:N/AC:L/PR:N/UI:R/S:C/C:H/I:L/A:N
Primary rating from NVD · only source for this CVE.
CVSS VectorNVD
DescriptionNVD
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.
Threat Intelligence Overview
NVD
CVE.org
EPSS
GitHub
How this decision was reached
The engine reads each signal below and applies a fixed list of rules from top to bottom. The first rule that matches sets the recommended action – like a statement, every line is shown.
What every action level means
SSVC AssessmentENISA
Priority Score
Attack Technique
Cross-Site Scripting occurs when an application accepts untrusted data and sends it to a web browser without proper validation or encoding.
Cross-Site Request Forgery exploits the automatic credential inclusion behavior of web browsers.
Affected Products (CPE)NVD
A specially crafted IOCTL can be issued to the rzpnk.sys driver in Razer Synapse 2.20.15.1104 that is forwarded to ZwOpe
In Apache Synapse, by default no authentication is required for Java Remote Method Invocation (RMI). Rated critical seve
Matrix Synapse before 1.5.0 mishandles signature checking on some federation APIs. Rated critical severity (CVSS 9.8), t
Multiple system services installed alongside the Razer Synapse 3 software suite perform privileged operations on entries
Multiple system services installed alongside the Razer Synapse 3 software suite perform privileged operations on entries
Matrix Synapse before 0.33.3.1 allows remote attackers to spoof events and possibly have unspecified other impacts by le
Synapse is an open source Matrix homeserver implementation. Rated high severity (CVSS 7.1), this vulnerability is remote
Razer Synapse 2.20.15.1104 and earlier uses weak permissions for the CrashReporter directory, which allows local users t
Synapse is an open-source Matrix homeserver written and maintained by the Matrix.org Foundation. Rated medium severity (
Local privilege escalation in Razer Synapse 3 lets an attacker who already holds a low-privileged foothold on a Windows
Local privilege escalation in Razer Synapse 3 allows an attacker who already holds a low-privileged foothold on a Window
Local privilege escalation in Razer Synapse 3 lets an attacker who already has low-privileged code execution on a Window
Exploit-DB