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Fencer Vulns
critical 9.8

CVE-2021-42343 json

Duplicate Advisory: Remote code execution in dask

published 2021-10-26 5 y ago modified 2026-07-09 4 mo ago also GHSA-hwqr-f3v9-hwxr , GHSA-j8fq-86c5-5v2r , PYSEC-2021-387 , PYSEC-2021-871 , PYSEC-2021-872 , EUVD-2021-0050

cvss
9.8
version 3.1, NVD
cisa kev
Not listed
not in CISA's catalog
epss
3.0%
EPSS 3.0% chance of exploitation in 30 days, percentile 87%
public exploits
0
none known

Summary

An issue was discovered in the Dask distributed package before 2021.10.0 for Python. Single machine Dask clusters 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 (when running on a machine that has an applicable port exposed) could be used by a sophisticated attacker to achieve remote code execution.

Patch / fix

  • pypi distributed 2021.10.0
  • pypi dask 2021.10.0
  • anaconda dask 2021.10.0
  • dask.distributed Debian 14, Debian 13, Debian 12 2021.09.1+ds.1-2

debian advisories DEBIAN-CVE-2021-42343

  • python-distributed openSUSE Tumbleweed 2026.6.0-1.1
  • python-distributed openSUSE Tumbleweed 2022.1.0-1.1
  • python-distributed openSUSE Tumbleweed 2024.4.2-1.1

opensuse advisories openSUSE-SU-2026:11043-1openSUSE-SU-2024:11766-1openSUSE-SU-2024:13920-1

  • py3-dask Alpine 3.24, Alpine 3.23, Alpine 3.22 +6 more 2022.2.0-r0

alpine advisories ALPINE-CVE-2021-42343

Alpine secdb © Alpine Linux, from https://secdb.alpinelinux.org via OSV; changed: normalised to fixed package versions per release. CC BY-SA 4.0

  • python-dask Arch Linux 2021.10.0-1

arch linux advisories AVG-2496

Vendor advisories

What the vendors themselves say about their products: affected, fixed or not affected, and what to do.

red hat product security vex CVE-2021-42343 updated cvss 9.8

python-dask: workers listen on external interfaces rather than only localhost

  • Red Hat All currently supported Red Hat products
    not affected: vulnerable code not present

Red Hat CSAF VEX © Red Hat, Inc., from https://security.access.redhat.com/data/csaf/v2/vex/; changed: reduced to product statuses and remediations. CC BY 4.0 · csaf

Exploit prediction

2.98% chance of exploitation in the next 30 days, higher than 87% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by version score vector
NVD 3.1 9.8 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
NVD 2.0 6.8 AV:N/AC:M/Au:N/C:P/I:P/A:P
GitHub 3.1 9.8 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

Affected packages

ecosystem package affected fixed in
pypi distributed
<2021.10.0
2021.10.0
pypi dask
<2021.10.0
2021.10.0

Classification

Weakness
  • CWE-668 Exposure of Resource to Wrong Sphere

References

Sources

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.