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CVE-2021-42387

27
FAUCET Score

CVE-2021-42387 is a high-severity heap out-of-bounds read vulnerability in ClickHouse's LZ4 compression codec, affecting various ClickHouse and Debian distributions. An authenticated attacker can trigger this by submitting a malicious query, leading to potential information disclosure and denial of service. While no public exploits or active exploitation have been observed, and community discussion is minimal, the vulnerability carries a CVSS score of 8.1.

Impacted Technologies

VendorProductVersion(s)CPE
< 21.10.2.15CPE matchmatch criteria
cpe:2.3:a:clickhouse:clickhouse:*:*:*:*:*:*:*:*
10.0CPE matchmatch criteria
cpe:2.3:o:debian:debian_linux:10.0:*:*:*:*:*:*:*

CVSS Data

CVSS version used by this source: 3.1

8.1HIGH

CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:H

Attack Vector
NETWORK
Attack Complexity
LOW
Privileges Required
LOW
User Interaction
NONE
Scope
UNCHANGED
Confidentiality Impact
HIGH
Integrity Impact
NONE
Availability Impact
HIGH
Exploitability Score
2.8
Impact Score
5.2
CvssVersion
3.1

Exploit Intelligence

EPSS Score
1.55%
Probability of exploitation in next 30 days
EPSS Percentile
72.5%
Percentile rank of EPSS score among Peer Group
As of 2026-07-27
Model: v2026.06.15
This CVE's current EPSS score of 0.0155 is in the 70th percentile among its peer group of 17,829 CVEs.

Social Chatter

The average CVE in this peer group has 0.0 Twitter, 0.0 Reddit, 0.3 Bluesky, 0.1 Mastodon, and 0.2 GitHub mentions.

Media Mentions

No media coverage found for this CVE.

The average CVE in this peer group has 0.1 InfoSec Media, 0.0 Vendor Blog, and 0.0 Security Researcher mentions.

Remediation

Remediation records are not available for this CVE.

References

jfrog.com / blog/7-rce-and-dos-vulnerabilities-found-in-clickhouse-dbms
ExploitThird Party Advisory
lists.debian.org / debian-lts-announce/2022/11/msg00002.html
Mailing ListThird Party Advisory