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No exploitation reportedFix available

CVE-2021-42387

No exploitation reported by the sources we read.

  • Published2022-03-14
  • Fixed in21.10.2.15
  • WeaknessCWE-125

Am I affected?

With a domain, we read the version its public headers and pages expose. A distribution build can carry the fix under an older number.

Description

Heap out-of-bounds read in Clickhouse's LZ4 compression codec when parsing a malicious query. As part of the LZ4::decompressImpl() loop, a 16-bit unsigned user-supplied value ('offset') is read from the compressed data. The offset is later used in the length of a copy operation, without checking the upper bounds of the source of the copy operation.

Timeline

dates in UTC
  1. 2022-03-1423:15CVE publishedNVD

Versions per branch

NVD
Clickhouse
BranchAffectedFixed in
21.10< 21.10.2.1521.10.2.15
Debian debian linux
BranchAffectedFixed in
10.0= 10.0no fix published

as publishedRanges as NVD and OSV publish them; a distribution’s build can be fixed under an older number.

Distribution builds and vendor advisories

Packages from OSV.dev and products from the vendors' CSAF advisories.

version not verifiedVersions not verified: read as OSV.dev and the vendors publish them, not checked against each vendor's release list.

Packages

  • clickhouseUbuntu:20.04:LTSall versions · fixed in 18.16.1+ds-7ubuntu0.1
  • clickhouseDebian:12all versions · fixed in 18.16.1+ds-7.3
  • clickhouseDebian:10all versions · fixed in 18.16.1+ds-4+deb10u1

Full record on NVD

Fix

  1. Update Clickhouse to 21.10.2.15

Detection

Nuclei template
none so far
ProjectDiscovery
Exploit-DB
no entry
Exploit-DB
Proof of concept
Metasploit modules
none listed
Metasploit Framework

Sources

  • NVDCVSS 3.18.1read 2026-10-23
  • NVDCVSS 2.05.5read 2026-10-23
  • CNAweakness (CWE)CWE-125known since 2026-10-23
  • NVDweakness (CWE)CWE-125read 2026-10-23
  • FIRST EPSSEPSS score1.6 %2026-11-08
  • OSVaffected packages—
  • GitHub Advisoriesadvisory—

Identifiers

Technical details

CVSS v3 Vector
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:H
Published
2022-03-14
Last Modified
2026-06-17
NVD status
Modified
GitHub Advisory
GHSA-cf9g-639p-3wvv

Frequently asked questions

What is CVE-2021-42387?

Heap out-of-bounds read in Clickhouse's LZ4 compression codec when parsing a malicious query. As part of the LZ4::decompressImpl() loop, a 16-bit unsigned user-supplied value ('offset') is read from the compressed data. The offset is later used in the length of a copy operation, without checking the upper bounds of the source of the copy operation.

Is CVE-2021-42387 actively exploited?

Active exploitation of CVE-2021-42387 has not been confirmed. Its EPSS score was 1.6% on 2026-11-08, the estimated probability of exploitation in the next 30 days.

What is the CVSS score for CVE-2021-42387?

CVE-2021-42387 has a CVSS v3 base score of 8.1 (HIGH severity), with vector string CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:H.

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