CVE-2021-46879Public exploit

Code execution via wrong MessagePack object dereference

Published Apr 11, 2023 · Updated Feb 11, 2025

Out-of-bounds write in Treasure Data Fluent Bit 1.7.1 allows local users to execute arbitrary code when a crafted file is opened. In flb_msgpack_gelf_value_ext, the GELF MessagePack extension branch reads the pointer and length from the outer object o instead of the current value v, causing an invalid heap access. Exploitation requires local access and user interaction; successful memory corruption runs code in the Fluent Bit process context.

CVSS severity7.8
High
EPSS probability0.38%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Out-of-bounds write in Treasure Data Fluent Bit 1.7.1 allows local users to execute arbitrary code when a crafted file is opened. In flb_msgpack_gelf_value_ext, the GELF MessagePack extension branch reads the pointer and length from the outer object o instead of the current value v, causing an invalid heap access. Exploitation requires local access and user interaction; successful memory corruption runs code in the Fluent Bit process context.

The record

CVE
CVE-2021-46879
Published
Apr 11, 2023
Updated
Feb 11, 2025
Vendor
Unknown vendor
Product
Unknown product
Classifications
CWE-787, T1203, T1204.002
Attack vector
local
Privileges
unauthenticated

Timeline

How it unfolded

  1. Apr 11, 2023CVE publishedPublication date reported by the CVE source.
  2. Feb 11, 2025Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Affected buildAffected product and version details are unavailable.

What conditions does exploitation require?

Attack vectorlocal
Required privilegesunauthenticated

What is affected?

Affected products and versions are unavailable in this record.

Published CVSS scores

7.8NIST NVDCVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H
7.8CISA-ADPCVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 9, 2026Sep 15, 2026
Latest reporting daySep 15, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectorlocal
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

CWE-787Out-of-bounds Write
T1203Exploitation for Client Execution
T1204.002Malicious File

Public exploit references

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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