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Vulnerability record · CVE-2021-46878 · published 11 April 2023

CVE-2021-46878: Treasuredata fluent bit type confusion vulnerability

Treasuredata · Fluent Bit

An issue was discovered in Treasure Data Fluent Bit 1.7.1, erroneous parsing in flb_pack_msgpack_to_json_format leads to type confusion bug that interprets whatever is on the stack as msgpack maps and arrays, leading to use-after-free. This can be used by an attacker to craft a specially craft file and trick the victim opening it using the affect software, triggering use-after-free and execute arbitrary code on the target system.

7.8 CVSS 3.1 High EPSS 0.35% · top 73.9% CWE-843 · Type confusion
7.8CVSS 3.1 base score
0.35%EPSS exploitation probability, 30 days
NoNot in CISA KEV
1Affected product versions listed by NVD
4References, 2 tagged exploit
17 Jun 2026Last modified by NVD

Description

An issue was discovered in Treasure Data Fluent Bit 1.7.1, erroneous parsing in flb_pack_msgpack_to_json_format leads to type confusion bug that interprets whatever is on the stack as msgpack maps and arrays, leading to use-after-free. This can be used by an attacker to craft a specially craft file and trick the victim opening it using the affect software, triggering use-after-free and execute arbitrary code on the target system.

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

Affected products

1 vulnerable configurations from NVD's CPE data, grouped by vendor and product.

References

LinkTags
https://bugs.chromium.org/p/oss-fuzz/issues/detail?id=27742 ExploitIssue TrackingPatchThird Party Advisory
https://github.com/fluent/fluent-bit/pull/3115 Patch
https://bugs.chromium.org/p/oss-fuzz/issues/detail?id=27742 ExploitIssue TrackingPatchThird Party Advisory
https://github.com/fluent/fluent-bit/pull/3115 Patch

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Related vulnerabilities

Same products first, then exploited flaws of the same weakness class.

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Source: NIST National Vulnerability Database (record CVE-2021-46878), CISA KEV, FIRST EPSS (scores of 2026-09-27). This page is refreshed as NVD updates the record.