DaskApplication · Anaconda
CVE-2021-42343
Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.
NVD · uneditedAn 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.
Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.
dbcve analysis · high confidenceDask LocalCluster and Client (default) misconfigure worker listeners to bind to all interfaces (0.0.0.0) instead of localhost only, exposing the high random port to external networks. This allows remote attackers to send malicious tasks to workers and achieve remote code execution.
Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.
Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.
NVD · CPE data
DaskApplication
< 2021.10.0CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.
From the vector- Attack vector
- Network
- Complexity
- Low
- Privileges
- None
- User interaction
- None
- Scope
- Unchanged
- Confidentiality
- High
- Integrity
- High
- Availability
- High
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.
dbcve checksWork through these to decide whether this CVE applies to you.
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Identify Dask installation and versionRun 'pip show dask' or 'conda list dask' to find the installed version of dask.distributedAffected if The installed version is before 2021.10.0 (e.g., 2021.9.0 or earlier)
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Confirm LocalCluster or default Client is in useInspect Python code or startup scripts for 'dask.distributed.LocalCluster()' or 'dask.distributed.Client()' usage without custom scheduler/worker argumentsAffected if Code creates a LocalCluster or uses the default Client without specifying host/bind_address parameters
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Check worker network binding configurationInspect running Dask worker processes using 'netstat -tnlp' or 'ss -tnlp' to see if workers are listening on 0.0.0.0 rather than 127.0.0.1Affected if Workers show bindings to 0.0.0.0 or external IP addresses rather than only 127.0.0.1
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Verify network exposureCheck firewall rules and whether the Dask host is directly accessible from untrusted networks; attempt external connection to worker ports from an untrusted hostAffected if The host has open ports reachable from networks where untrusted users reside
You are affected if running Dask version before 2021.10.0 with LocalCluster or default Client, and workers are binding to 0.0.0.0 on externally accessible networks.
Generated from the published advisory. Verify against your own configuration.
Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.
dbcve · scoped2021.10.0
Upgrade dask.distributed to version 2021.10.0 or later, or explicitly configure workers to listen only on 127.0.0.1; ensure Dask clusters are not exposed to untrusted networks.
2021.10.0
- Upgrade Dask to version 2021.10.0 or later using pip: pip install 'dask>=2021.10.0' or conda: conda install 'dask>=2021.10.0'
- If using a requirements file, update the dask dependency to >=2021.10.0
- Restart any Dask services (LocalCluster, Client, workers) to load the updated version
- Verify the fix by confirming workers bind to localhost only (127.0.0.1) rather than external interfaces
Generated from the published advisory — verify against the referenced sources before acting.
Fix this in Dask
Scoped from the published advisory
- Consultation4.0 h
- Implementation6.0 h
- Testing4.0 h
- Review / QA2.0 h
An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $4,544.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2021-42343 — or any other known-vulnerable package — straight from your lock files. Free and open source; it runs locally and uploads nothing.
References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.
Primary sourcesPractitioner notes
ContributedPeer-ranked notes from engineers who’ve handled CVE-2021-42343 in production — separate from our analysis above.
The advisory tells you what broke. It rarely tells you what actually worked. If you’ve dealt with this one, that detail is what the next engineer is searching for.
- The version that genuinely resolved it — not the one the vendor claimed
- A config change or rule that shut the vector down
- A gotcha in the upgrade path that cost you an afternoon
No notes yet
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- Version or environment caveats, and links to real fixes
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