How severe is CVE-2021-43305?

CVE-2021-43305 has a CVSS 3.x base score of 8.8, rated high severity. It is exploitable over network with low attack complexity, requires low privileges and no user interaction. Impact on confidentiality is high, integrity high, and availability high.

Is CVE-2021-43305 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 2% (74th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2021-43305?

CVE-2021-43305 primarily affects Clickhouse. In total, 2 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.

How do I fix CVE-2021-43305?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its high severity, prioritise patching exposed systems.

When was CVE-2021-43305 published?

CVE-2021-43305 was published on 2022-03-14 and last updated on 2026-06-17.

CVE-2021-43305

CVE-2021-43305 is a high-severity vulnerability in Clickhouse with a CVSS 3.x base score of 8.8. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-787.

Key facts

Severity: High (CVSS 3.x base score 8.8)
CVSS v2: 6.5
EPSS exploit prediction: 2% (74th percentile)
Actively exploited: Not listed in CISA KEV
Weakness: CWE-787
Affected product: Clickhouse
Published: 2022-03-14
Last modified: 2026-06-17

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. This issue is very similar to CVE-2021-43304, but the vulnerable copy operation is in a different wildCopy call.

Frequently asked questions

What is CVE-2021-43305?: 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.
How severe is CVE-2021-43305?: CVE-2021-43305 has a CVSS 3.x base score of 8.8, rated high severity. It is exploitable over network with low attack complexity, requires low privileges and no user interaction. Impact on confidentiality is high, integrity high, and availability high.
Is CVE-2021-43305 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 2% (74th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2021-43305?: CVE-2021-43305 primarily affects Clickhouse. In total, 2 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.
How do I fix CVE-2021-43305?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its high severity, prioritise patching exposed systems.
When was CVE-2021-43305 published?: CVE-2021-43305 was published on 2022-03-14 and last updated on 2026-06-17.

References

Affected products (2)

cpe:2.3:a:clickhouse:clickhouse:*:*:*:*:*:*:*:*
cpe:2.3:o:debian:debian_linux:10.0:*:*:*:*:*:*:*

More vulnerabilities in Clickhouse

CVE-2019-16535 — Critical (CVSS 9.8): In all versions of ClickHouse before 19.14, an OOB read, OOB write and integer underflow in decompression algorithms…
CVE-2018-14671 — Critical (CVSS 9.8): In ClickHouse before 18.10.3, unixODBC allowed loading arbitrary shared objects from the file system which led to a…
CVE-2018-14670 — Critical (CVSS 9.8): Incorrect configuration in deb package in ClickHouse before 1.1.54131 could lead to unauthorized use of the database.
CVE-2019-16536 — High (CVSS 8.8): Stack overflow leading to DoS can be triggered by a malicious authenticated client in Clickhouse before 19.14.3.3.
CVE-2021-43304 — High (CVSS 8.8): Heap buffer overflow in Clickhouse's LZ4 compression codec when parsing a malicious query. There is no verification…
CVE-2018-14668 — High (CVSS 8.8): In ClickHouse before 1.1.54388, "remote" table function allowed arbitrary symbols in "user", "password" and…

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