{"id":"CVE-2021-42343","aliases":["GHSA-hwqr-f3v9-hwxr","GHSA-j8fq-86c5-5v2r","PYSEC-2021-387","PYSEC-2021-871","PYSEC-2021-872"],"title":"Workers for local Dask clusters mistakenly listened on public interfaces","summary":"Workers for local Dask clusters mistakenly listened on public interfaces","severity":"critical","cvss":9.8,"cvssVector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H","vendor":"distributed","product":"distributed","ecosystem":"pip","affected":["distributed < 2021.10.0"],"patched":["distributed 2021.10.0"],"published":"2022-07-15","updated":"2026-07-08","source":"OSV","sourceUrl":"https://osv.dev/vulnerability/GHSA-hwqr-f3v9-hwxr","references":[{"url":"https://github.com/dask/distributed/security/advisories/GHSA-hwqr-f3v9-hwxr"},{"url":"https://nvd.nist.gov/vuln/detail/CVE-2021-42343"},{"url":"https://github.com/dask/distributed/pull/5427"},{"url":"https://github.com/dask/distributed/commit/afce4be8e05fb180e50a9d9e38465f1a82295e1b"},{"url":"https://docs.dask.org/en/latest/changelog.html"},{"url":"https://github.com/dask/dask/tags"},{"url":"https://github.com/dask/distributed"},{"url":"https://github.com/pypa/advisory-database/tree/main/vulns/distributed/PYSEC-2021-871.yaml"},{"url":"https://github.com/pypa/advisory-database/tree/main/vulns/distributed/PYSEC-2021-872.yaml"}],"tags":["osv","pip"],"epss":0.02995,"epssPercentile":0.86772,"ingestedAt":"2026-07-08T18:25:50.334Z","slug":"CVE-2021-42343","body":"## Overview\n\nVersions 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).\n\n## Affected packages\n\n- `distributed < 2021.10.0`\n\n## Remediation\n\nUpgrade to a patched release:\n\n- `distributed 2021.10.0`","depth":"midnight","depthScore":54,"depthScoreParts":{"impact":53.9,"likelihood":0.6,"exploitation":0,"ransomware":0},"changes":[]}