CVE-2020-35963

Severity: high (CVSS 7.8 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 1.3% probability of exploitation in the next 30 days
Public exploit or detection template: yes
Published: 2021-01-03 · updated 2026-06-17
Weakness: CWE-787

Description

flb_gzip_compress in flb_gzip.c in Fluent Bit before 1.6.4 has an out-of-bounds write because it does not use the correct calculation of the maximum gzip data-size expansion.

Affected products

FluentBit Fluent Bit: before 1.6.4 — fixed in 1.6.4

How to fix

Upgrade to a fixed version: FluentBit Fluent Bit 1.6.4. Check the vendor advisory for mitigations.

References

https://bugs.chromium.org/p/oss-fuzz/issues/detail?id=27261
https://fluentbit.io/announcements/v1.6.4/
https://github.com/fluent/fluent-bit/commit/cadff53c093210404aed01c4cf586adb8caa07af
https://bugs.chromium.org/p/oss-fuzz/issues/detail?id=27261
https://fluentbit.io/announcements/v1.6.4/
https://github.com/fluent/fluent-bit/commit/cadff53c093210404aed01c4cf586adb8caa07af

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