CVE-2021-42388Network attack vector

Authenticated disclosure or crash via unchecked LZ4 offset

Published Mar 14, 2022 · Updated Aug 4, 2024

Out-of-bounds read in ClickHouse before 21.10.2.15-stable allows remote authenticated users to crash the server via a malicious query. In LZ4::decompressImpl(), an unchecked 16-bit offset is subtracted from the destination pointer and then used as the source of a copy. Any account with read permission can reach the codec; an out-of-range match pointer reads preceding heap memory, enabling disclosure or a segmentation-fault crash.

CVSS severity8.1
High
EPSS probability1.57%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Out-of-bounds read in ClickHouse before 21.10.2.15-stable allows remote authenticated users to crash the server via a malicious query. In LZ4::decompressImpl(), an unchecked 16-bit offset is subtracted from the destination pointer and then used as the source of a copy. Any account with read permission can reach the codec; an out-of-range match pointer reads preceding heap memory, enabling disclosure or a segmentation-fault crash.

The record

CVE
CVE-2021-42388
Published
Mar 14, 2022
Updated
Aug 4, 2024
Vendor
ClickHouse
Product
ClickHouse
Classifications
CWE-125, CAPEC-540, T1499.004
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

8.1NIST NVDCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:H
5.5NIST NVDAV:N/AC:L/Au:S/C:P/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.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

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-125Out-of-bounds Read
CAPEC-540Overread Buffers
T1499.004Endpoint Denial of Service: Application or System Exploitation

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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