{"cve":"CVE-2021-29431","nvd":{"published":"2021-04-15T21:15:17.520","modified":"2026-06-17T03:47:37.687","status":"Modified","description":"Sydent is a reference Matrix identity server. Sydent can be induced to send HTTP GET requests to internal systems, due to lack of parameter validation or IP address blacklisting. It is not possible to exfiltrate data or control request headers, but it might be possible to use the attack to perform an internal port enumeration. This issue has been addressed in in 9e57334, 8936925, 3d531ed, 0f00412. A potential workaround would be to use a firewall to ensure that Sydent cannot reach internal HTTP resources.","cvss_v4":null,"cvss_v3":{"version":"3.1","vector":"CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N","score":6.5},"cwes":["CWE-20","CWE-918"],"references":["https://github.com/matrix-org/sydent/commit/0f00412017f25619bc36c264b29ea96808bf310a","https://github.com/matrix-org/sydent/commit/3d531ed50d2fd41ac387f36d44d3fb2c62dd22d3","https://github.com/matrix-org/sydent/commit/8936925f561b0c352c2fa922d5097d7245aad00a","https://github.com/matrix-org/sydent/commit/9e573348d81df8191bbe8c266c01999c9d57cd5f","https://github.com/matrix-org/sydent/releases/tag/v2.3.0"],"products":["matrix:sydent"],"source":"nvd","synced_at":"2026-10-19T21:17:01.373894544+00:00"},"epss":{"cve":"CVE-2021-29431","score":0.01194,"percentile":0.68038,"date":"2026-11-01"},"kev":null,"osv":[{"id":"GHSA-9jhm-8m8c-c3f4","url":"https://osv.dev/vulnerability/GHSA-9jhm-8m8c-c3f4","summary":"SSRF in Sydent due to missing validation of hostnames","modified":"2026-09-10T03:49:03.074179988Z","packages":[{"ecosystem":"PyPI","name":"matrix-sydent","purl":"pkg:pypi/matrix-sydent","ranges":["<2.3.0"],"fixed":["2.3.0"]}]},{"id":"PYSEC-2021-22","url":"https://osv.dev/vulnerability/PYSEC-2021-22","summary":"","modified":"2023-11-08T04:05:33.712503Z","packages":[{"ecosystem":"PyPI","name":"matrix-sydent","purl":"pkg:pypi/matrix-sydent","ranges":["<2.3.0"],"fixed":["2.3.0"]}]}],"attribution":["This product uses the NVD API but is not endorsed or certified by the NVD.","EPSS scores: FIRST Exploit Prediction Scoring System, https://www.first.org/epss","Known exploited vulnerabilities: CISA Known Exploited Vulnerabilities Catalog, https://www.cisa.gov/known-exploited-vulnerabilities-catalog","Package advisories: OSV (https://osv.dev), from the GitHub Advisory Database, PyPA, Go, RustSec and other ecosystem databases, under CC-BY 4.0 or CC0","CVE records: the CVE Program's CVE List (https://www.cve.org), under its terms of use (https://www.cve.org/Legal/TermsOfUse). CVE is a registered trademark of The MITRE Corporation; this product is not affiliated with the CVE Program."]}