{"id":"CVE-2021-42343","aliases":["GHSA-hwqr-f3v9-hwxr","GHSA-j8fq-86c5-5v2r","PYSEC-2021-387","PYSEC-2021-871"],"url":"https://o3.security/vulnerability/CVE-2021-42343","summary":"Workers for local Dask clusters mistakenly listened on public interfaces","details":"Versions of `distributed` earlier than `2021.10.0` had a potential security vulnerability relating to single-machine Dask clusters.\n\nClusters started with `dask.distributed.LocalCluster` or `dask.distributed.Client()` (which defaults to using `LocalCluster`) would mistakenly configure their respective Dask workers to listen on external interfaces (typically with a randomly selected high port) rather than only on `localhost`. A Dask cluster created using this method AND running on a machine that has these ports exposed could be used by a sophisticated attacker to enable remote code execution. Users running on machines with standard firewalls in place, or using clusters created via cluster objects other than `LocalCluster` (e.g. `dask_kubernetes.KubeCluster`) should not be affected. This vulnerability is documented in CVE-2021-42343, and was fixed in version `2021.10.0` (PR #5427).","published":"2021-10-26T11:15:07.800Z","modified":"2026-08-07T16:57:52.106314Z","cvss":{"score":9.8,"severity":"CRITICAL","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H"},"epss":{"score":0.02995,"percentile":0.86266,"asOf":"2026-08-23"},"cisaKev":null,"exploitsKnown":0,"affectedPackages":[{"ecosystem":"PyPI","name":"distributed","fixedVersion":"2021.10.0"}],"fix":{"url":"https://github.com/dask/distributed/pull/5427","label":"dask/distributed#5427"},"references":[{"type":"ADVISORY","url":"https://docs.dask.org/en/latest/changelog.html"},{"type":"ADVISORY","url":"https://github.com/dask/dask/tags"},{"type":"ADVISORY","url":"https://github.com/dask/distributed/security/advisories/GHSA-hwqr-f3v9-hwxr"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2021-42343"},{"type":"WEB","url":"https://github.com/dask/distributed/pull/5427"},{"type":"WEB","url":"https://github.com/dask/distributed/commit/afce4be8e05fb180e50a9d9e38465f1a82295e1b"},{"type":"PACKAGE","url":"https://github.com/dask/distributed"},{"type":"WEB","url":"https://github.com/pypa/advisory-database/tree/main/vulns/distributed/PYSEC-2021-871.yaml"},{"type":"WEB","url":"https://github.com/pypa/advisory-database/tree/main/vulns/distributed/PYSEC-2021-872.yaml"}],"provenance":{"sources":["OSV.dev","FIRST.org (EPSS)"],"lastVerified":"2026-08-07T16:57:52.106314Z"}}