CVE-2021-42390Network attack vector

Authenticated DoS via unchecked DeltaDouble divisor

Published Mar 14, 2022 · Updated Aug 4, 2024

ClickHouse before 21.10.2.15 allows remote authenticated users to interrupt service with a malicious query targeting the DeltaDouble compression codec. The parser uses the first compressed-buffer byte as a modulo divisor without checking for zero, causing a divide-by-zero crash. Exploitation requires valid query authentication and reaches availability impact only; confidentiality and integrity are not affected.

CVSS severity6.5
Medium
EPSS probability1.26%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

ClickHouse before 21.10.2.15 allows remote authenticated users to interrupt service with a malicious query targeting the DeltaDouble compression codec. The parser uses the first compressed-buffer byte as a modulo divisor without checking for zero, causing a divide-by-zero crash. Exploitation requires valid query authentication and reaches availability impact only; confidentiality and integrity are not affected.

The record

CVE
CVE-2021-42390
Published
Mar 14, 2022
Updated
Aug 4, 2024
Vendor
ClickHouse
Product
ClickHouse
Classifications
CWE-369, T1499
Attack vector
network
Privileges
authenticated

Timeline

How it unfolded

  1. Mar 14, 2022CVE publishedPublication date reported by the CVE source.
  2. Aug 4, 2024Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=unspecified <21.10.2.15-stable

What conditions does exploitation require?

Attack vectornetwork
Required privilegesauthenticated

What is affected?

ClickHouse · ClickHouseversion=unspecified <21.10.2.15-stable

Published CVSS scores

6.5NVDCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
4.0NVDAV:N/AC:L/Au:S/C:N/I:N/A:P

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

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No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-369Divide By Zero
T1499Endpoint Denial of Service

Public exploit references

No public exploit references are available in this record.

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Technologies

Your stack

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Your stack

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