CVE-2021-42389
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 · uneditedDivide-by-zero in Clickhouse's Delta compression codec when parsing a malicious query. The first byte of the compressed buffer is used in a modulo operation without being checked for 0.
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 analysisA detailed technical summary for this CVE is being prepared.
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< 21.10.2.15CVSS 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
- Low
- User interaction
- None
- Scope
- Unchanged
- Confidentiality
- None
- Integrity
- None
- Availability
- High
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
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 · scoped21.10.2.15
21.10.2.15 or later (any version after 21.10.2.15 contains the fix)
- 1. Back up all Clickhouse data and configuration files before proceeding with the upgrade
- 2. Check the current installed version of Clickhouse using: systemctl status clickhouse-server or clickhouse-server --version
- 3. Update the Clickhouse package repository and upgrade to version 21.10.2.15 or later. For yum/dnf-based systems: sudo yum update clickhouse-server clickhouse-client clickhouse-common
- 4. For apt-based systems: sudo apt-get update && sudo apt-get install clickhouse-server=21.10.2.15 clickhouse-client=21.10.2.15 clickhouse-common=21.10.2.15
- 5. Restart the Clickhouse service: sudo systemctl restart clickhouse-server
- 6. Verify the upgrade was successful by running: clickhouse-server --version
- 7. Test that queries using Delta compression codec work correctly
Generated from the published advisory — verify against the referenced sources before acting.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2021-42389 — 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-2021-42389 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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- Verified mitigations, workarounds, and config changes
- Version or environment caveats, and links to real fixes
- No weaponised exploit code, or anything meant to cause harm
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