{"id":"GHSA-wmg4-8cp2-hpg9","summary":"Sydent vulnerable to denial of service attack via memory exhaustion","details":"### Impact\n\nSydent 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 disk space exhaustion and denial of service.\n\nSydent 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.\n\nThis affects any server which accepts registration requests from untrusted clients.\n\n### Patches\n\nPatched by 89071a1, 0523511, f56eee3.\n\n### Workarounds\n\nRequest sizes can be limited in an HTTP reverse-proxy.\n\nThere are no known workarounds for the problem with overlarge responses.\n\n### For more information\n\nIf you have any questions or comments about this advisory, email us at security@matrix.org.","aliases":["CVE-2021-29430","PYSEC-2021-21"],"modified":"2026-05-07T05:01:57.918835875Z","published":"2021-04-19T14:54:04Z","database_specific":{"severity":"HIGH","github_reviewed":true,"github_reviewed_at":"2021-04-15T20:49:34Z","nvd_published_at":"2021-04-15T21:15:00Z","cwe_ids":["CWE-20","CWE-400","CWE-770"]},"references":[{"type":"WEB","url":"https://github.com/matrix-org/sydent/security/advisories/GHSA-wmg4-8cp2-hpg9"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2021-29430"},{"type":"WEB","url":"https://github.com/matrix-org/sydent/commit/0523511d2fb40f2738f8a8549868f44b96e5dab7"},{"type":"WEB","url":"https://github.com/matrix-org/sydent/commit/89071a1a754c69a50deac89e6bb74002d4cda19d"},{"type":"WEB","url":"https://github.com/matrix-org/sydent/commit/f56eee315b6c44fdd9f6aa785cc2ec744a594428"},{"type":"PACKAGE","url":"https://github.com/matrix-org/sydent"},{"type":"WEB","url":"https://github.com/matrix-org/sydent/releases/tag/v2.3.0"},{"type":"WEB","url":"https://github.com/pypa/advisory-database/tree/main/vulns/matrix-sydent/PYSEC-2021-21.yaml"},{"type":"WEB","url":"https://pypi.org/project/matrix-sydent"}],"affected":[{"package":{"name":"matrix-sydent","ecosystem":"PyPI","purl":"pkg:pypi/matrix-sydent"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"2.3.0"}]}],"versions":["2.0.0","2.0.1","2.1.0","2.2.0"],"database_specific":{"source":"https://github.com/github/advisory-database/blob/main/advisories/github-reviewed/2021/04/GHSA-wmg4-8cp2-hpg9/GHSA-wmg4-8cp2-hpg9.json"}}],"schema_version":"1.9.0","severity":[{"type":"CVSS_V3","score":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H"},{"type":"CVSS_V4","score":"CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N"}]}