CVE-2021-43304
CVSS v3
8.8
HIGH
EPSS Score
1.7 %
exploit probability, as of 2026-09-25
CISA KEV
No
known exploited
Exploitation
—
SSVC status
Description
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.
Technical details
- Published
- 2022-03-14
Frequently asked questions
What is CVE-2021-43304?
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.
Is CVE-2021-43304 actively exploited?
Active exploitation of CVE-2021-43304 has not been confirmed. Its EPSS score was 1.7% on 2026-09-25, the estimated probability of exploitation in the next 30 days.
What is the CVSS score for CVE-2021-43304?
CVE-2021-43304 has a CVSS v3 base score of 8.8 (HIGH severity).
Is CVE-2021-43304 affecting your environment?
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