CVE-2020-35963

Name: CVE-2020-35963
Creator: NVD / NIST
Published: 2021-01-03T19:15:11.673+00:00
License: https://creativecommons.org/publicdomain/zero/1.0/

HIGHCVSS 7.8/10EPSS 1.31%

Last modified Jun 17, 2026

CVE-2020-35963 is a high-severity vulnerability rated 7.8/10 on the CVSS scale. 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.. EPSS estimates a 1.31% chance of exploitation in the next 30 days.

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.

Metrics

CVSS 3.1

7.8/10

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

EPSS Probability

1.31%

67.0th percentile

Probability of exploitation in the next 30 days. Learn more

Weakness Enumeration

CWE-787

Affected Software

Vendor	Product	Versions
Treasuredata	Fluent Bit	< 1.6.4

References

https://bugs.chromium.org/p/oss-fuzz/issues/detail?id=27261Exploit, Issue Tracking, Third Party Advisory
https://fluentbit.io/announcements/v1.6.4/Release Notes, Vendor Advisory
https://github.com/fluent/fluent-bit/commit/cadff53c093210404aed01c4cf586adb8caa07afPatch, Third Party Advisory
https://bugs.chromium.org/p/oss-fuzz/issues/detail?id=27261Exploit, Issue Tracking, Third Party Advisory
https://fluentbit.io/announcements/v1.6.4/Release Notes, Vendor Advisory
https://github.com/fluent/fluent-bit/commit/cadff53c093210404aed01c4cf586adb8caa07afPatch, Third Party Advisory

Timeline

Published: Jan 3, 2021
Last Modified: Jun 17, 2026
Status: Modified

Frequently Asked Questions

What is CVE-2020-35963?

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.

How severe is CVE-2020-35963?

CVE-2020-35963 has a CVSS score of 7.8/10 (HIGH severity). The EPSS model estimates a 1.31% probability of exploitation in the next 30 days.

How do I fix CVE-2020-35963?

Check the vendor references and advisories linked above for patched versions and mitigation guidance. You can also run a Strix scan to test if your systems are affected.

Are you affected by CVE-2020-35963?

Run a free Strix scan to check your systems for this vulnerability.

Scan your code now

Source: NVD / NIST