CVE-2021-29430

Advisory

Sydent 2.3.0 includes a fix for CVE-2021-29430: 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. As a workaround, request sizes can be limited in an HTTP reverse-proxy. There are no known workarounds for the problem with overlarge responses.

Affected package

Affected versions

Fixed versions

Vulnerability changelog

This vulnerability has no description

Resources

• https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2021-29430
• https://github.com/matrix-org/sydent/commit/0523511d2fb40f2738f8a8549868f44b96e5dab7
• https://github.com/matrix-org/sydent/commit/89071a1a754c69a50deac89e6bb74002d4cda19d
• https://github.com/matrix-org/sydent/commit/f56eee315b6c44fdd9f6aa785cc2ec744a594428
• https://github.com/matrix-org/sydent/security/advisories/GHSA-wmg4-8cp2-hpg9
• https://pypi.org/project/matrix-sydent/
• https://github.com/matrix-org/sydent/releases/tag/v2.3.0