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Fencer Vulns
high 8.8

CVE-2021-43305 json

Heap buffer overflow in Clickhouse's LZ4 compression codec when parsing a malicious query.

published 2022-03-14 4 y ago modified 2026-06-17 4 mo ago also EUVD-2021-30248

cvss
8.8
version 3.1, NVD
cisa kev
Not listed
not in CISA's catalog
epss
1.7%
EPSS 1.7% chance of exploitation in 30 days, percentile 76%
public exploits
0
none known

Summary

Heap buffer overflow in Clickhouse's LZ4 compression codec when parsing a malicious query. There is no verification that the copy operations in the LZ4::decompressImpl loop and especially the arbitrary copy operation wildCopy<copy_amount>(op, ip, copy_end), don’t exceed the destination buffer’s limits. This issue is very similar to CVE-2021-43304, but the vulnerable copy operation is in a different wildCopy call.

Patch / fix

  • yandex clickhouse 21.10.2.15-stable
  • clickhouse Debian 12 18.16.1+ds-7.3

debian advisories DEBIAN-CVE-2021-43305

  • clickhouse Ubuntu 20.04 LTS 18.16.1+ds-7ubuntu0.1

ubuntu advisories UBUNTU-CVE-2021-43305

Ubuntu security data © Canonical Ltd., from https://github.com/canonical/ubuntu-security-notices via OSV; changed: normalised to fixed package versions per release. CC BY-SA 4.0

Exploit prediction

1.67% chance of exploitation in the next 30 days, higher than 76% of all scored CVEs (FIRST EPSS, 2026-11-08).

Exploits and checks

  • jfrog.com https://jfrog.com/blog/7-rce-and-dos-vulnerabilities-found-in-clickhouse-dbms referenced PoC, tagged "exploit" by a source, unverified

CVSS scores

assigned by version score vector
NVD 3.1 8.8 CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
NVD 2.0 6.5 AV:N/AC:L/Au:S/C:P/I:P/A:P

Affected products

  • yandex clickhouse

Classification

Weakness

References

Sources

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.