CVE-2021-42387Network attack vector

Authenticated memory disclosure via unchecked LZ4 copy

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 disclose memory or interrupt service via a malicious query. The LZ4::decompressImpl() loop trusts a 16-bit offset from compressed query data and uses it to size a copy without checking source bounds. A user with query credentials can trigger the flaw over the network; consequences are memory disclosure and service interruption, with no integrity impact reported.

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

See if you're affected

Explore vulnerability checks for your environment with Hinoki.

Book a demo

Summary

What happened

Out-of-bounds read in ClickHouse before 21.10.2.15-stable allows remote authenticated users to disclose memory or interrupt service via a malicious query. The LZ4::decompressImpl() loop trusts a 16-bit offset from compressed query data and uses it to size a copy without checking source bounds. A user with query credentials can trigger the flaw over the network; consequences are memory disclosure and service interruption, with no integrity impact reported.

The record

CVE
CVE-2021-42387
Published
Mar 14, 2022
Updated
Aug 4, 2024
Vendor
ClickHouse
Product
ClickHouse
Classifications
CWE-125, T1210
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

Compare your product and version with the public record. A matching version still requires validation against your environment.

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

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

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
T1210Exploitation of Remote Services

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

See the directory against your own environment.

Your stack

Check the software in your environment

Book a demo to see how Hinoki identifies affected software and validates exploitability in your environment.

Book a demo