CVE-2021-39163
3.1 · LOWOverview
CVE-2021-39163 is a low-severity vulnerability affecting matrix synapse. It was published on August 31, 2021 and has a CVSS 3.1 base score of 3.1 (LOW).
This vulnerability has a CVSS 3.1 base score of 3.1, rated LOW. It can be exploited remotely over the network. Some level of privileges is required for exploitation.
Technical Description
Matrix is an ecosystem for open federated Instant Messaging and Voice over IP. In versions 1.41.0 and prior, unauthorised users can access the name, avatar, topic and number of members of a room if they know the ID of the room. This vulnerability is limited to homeservers where the vulnerable homeserver is in the room and untrusted users are permitted to create groups (communities). By default, only homeserver administrators can create groups. However, homeserver administrators can already access this information in the database or using the admin API. As a result, only homeservers where the configuration setting `enable_group_creation` has been set to `true` are impacted. Server administrators should upgrade to 1.41.1 or higher to patch the vulnerability. There are two potential workarounds. Server administrators can set `enable_group_creation` to `false` in their homeserver configuration (this is the default value) to prevent creation of groups by non-administrators. Administrators t
Remediation
Check the references section for vendor advisories and patches from matrix. Update synapse to the latest patched version. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.
Affected Products
| Vendor | Product | Versions | Status |
|---|---|---|---|
| matrix | synapse | >= 0, < 1.41.1 | Affected |
References
Frequently Asked Questions
What is CVE-2021-39163?
CVE-2021-39163 is a low-severity vulnerability affecting matrix synapse. It was published on August 31, 2021 and has a CVSS 3.1 base score of 3.1 (LOW).
How severe is CVE-2021-39163?
This vulnerability has a CVSS 3.1 base score of 3.1, rated LOW. It can be exploited remotely over the network. Some level of privileges is required for exploitation.
How do I fix or remediate CVE-2021-39163?
Check the references section for vendor advisories and patches from matrix. Update synapse to the latest patched version. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.
How can CyberStrike help with CVE-2021-39163?
CyberStrike's AI-powered security agents can automatically detect CVE-2021-39163 across your infrastructure using autonomous pentesting, DAST scanning, and HackBrowser. The platform continuously monitors for known vulnerabilities and provides actionable remediation guidance prioritized by real-world exploitability.
How CyberStrike Helps
AI agents map your attack surface to find vulnerabilities like this one.
Automated penetration testing that runs continuously, not just quarterly.
AI-driven PR review catches vulnerable dependencies before they ship.
Browser-based exploitation validates findings with real proof-of-concept.
Related LOW CVEs from 2021
View all →ide_atapi_cmd_reply_end in hw/ide/atapi.c in QEMU 5.1.0 allows out-of-bounds read access because a b
The ownCloud application before 2.15 for Android allows attackers to use adb to include a PIN prefer
fr-archive-libarchive.c in GNOME file-roller through 3.38.0, as used by GNOME Shell and other softwa
Vulnerability in the Hyperion Financial Management product of Oracle Hyperion (component: Task Autom
Improper Check for Unusual or Exceptional Conditions vulnerability exists in Triconex Model 3009 MP
Improper Check for Unusual or Exceptional Conditions vulnerability exists in Triconex TCM 4351B inst
Improper Check for Unusual or Exceptional Conditions vulnerability exists in Triconex Model 3009 MP
Improper Check for Unusual or Exceptional Conditions vulnerability exists in Triconex Model 3009 MP
Improper Check for Unusual or Exceptional Conditions vulnerability exists in Triconex Model 3009 MP
Improper Check for Unusual or Exceptional Conditions vulnerability exists in Triconex Model 3009 MP
Nextcloud Android app is the Android client for Nextcloud. In versions prior to 3.16.1, a malicious
Trusty TLK contains a vulnerability in its access permission settings where it does not properly res