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CVE-2021-29430

7.5 · HIGH

Sydent is a reference Matrix identity server.

Published Apr 15, 2021CWE-20EPSS 1.83%

Overview

CVE-2021-29430 is a high-severity vulnerability. It was published on April 15, 2021 and has a CVSS 3.1 base score of 7.5 (HIGH).

This vulnerability has a CVSS 3.1 base score of 7.5, rated HIGH. It can be exploited remotely over the network. No authentication or special privileges are required for exploitation.

Technical description

Sydent is a reference Matrix identity server. Sydent does not limit the size of requests it receives from HTTP clients. A malicious user could send an HTTP request with a very large body, leading to memory exhaustion and denial of service. Sydent also does not limit response size for requests it makes to remote Matrix homeservers. A malicious homeserver could return a very large response, again leading to memory exhaustion and denial of service. This affects any server which accepts registration requests from untrusted clients. This issue has been patched by releases 89071a1, 0523511, f56eee3. As a workaround request sizes can be limited in an HTTP reverse-proxy. There are no known workarounds for the problem with overlarge responses.

Remediation

Check the references section for vendor advisories, patches, and mitigation guidance. 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.

References

GitHubgithub.com/matrix-org/sydent/commit/0523511d2fb40f2738f8a8549868f44b96e5dab7GitHubgithub.com/matrix-org/sydent/commit/89071a1a754c69a50deac89e6bb74002d4cda19dGitHubgithub.com/matrix-org/sydent/commit/f56eee315b6c44fdd9f6aa785cc2ec744a594428GitHubgithub.com/matrix-org/sydent/releases/tag/v2.3.0GitHubgithub.com/matrix-org/sydent/security/advisories/GHSA-wmg4-8cp2-hpg9Refpypi.org/project/matrix-sydent/GitHubgithub.com/matrix-org/sydent/commit/0523511d2fb40f2738f8a8549868f44b96e5dab7GitHubgithub.com/matrix-org/sydent/commit/89071a1a754c69a50deac89e6bb74002d4cda19dGitHubgithub.com/matrix-org/sydent/commit/f56eee315b6c44fdd9f6aa785cc2ec744a594428GitHubgithub.com/matrix-org/sydent/releases/tag/v2.3.0

How CyberStrike helps

Frequently asked questions

What is CVE-2021-29430?

CVE-2021-29430 is a high-severity vulnerability. It was published on April 15, 2021 and has a CVSS 3.1 base score of 7.5 (HIGH).

How severe is CVE-2021-29430?

This vulnerability has a CVSS 3.1 base score of 7.5, rated HIGH. It can be exploited remotely over the network. No authentication or special privileges are required for exploitation.

How do I fix or remediate CVE-2021-29430?

Check the references section for vendor advisories, patches, and mitigation guidance. 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-2021-29430?

CyberStrike is an open-source, AI-augmented pentesting engine. Rather than flag a version number, it tests whether an issue like CVE-2021-29430 is actually reachable in your own applications and APIs, then verifies each finding before reporting it. That tells you if the weakness is a real, exploitable risk in your environment or a false positive you can safely deprioritize.

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