Fluentd: Remote Code Execution (RCE) via Arbitrary File Write in `${tag}` Placeholder

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Summary

CVECVE-2026-44024
StatePUBLISHED
AssignerGitHub_M
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-07-08 22:17:14 UTC
Updated2026-07-10 17:49:57 UTC
DescriptionFluentd collects events from various data sources and writes them to files, RDBMS, NoSQL, IaaS, SaaS, Hadoop and so on. Prior to 1.19.3, Fluentd allows dynamically constructing file paths using the ${tag} placeholder, and insufficient validation of ${tag} in file configurations such as the path parameter of the out_file plugin allows attackers sending untrusted tags containing path traversal characters to write or overwrite arbitrary files and potentially achieve remote code execution. This issue is fixed in version 1.19.3.

Risk And Classification

Primary CVSS: v3.1 9.8 CRITICAL from [email protected]

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

EPSS: 0.011070000 probability, percentile 0.619880000 (date 2026-07-11)

Problem Types: CWE-22 | CWE-22 CWE-22: Improper Limitation of a Pathname to a Restricted Directory ('Path Traversal')

VersionSourceTypeScoreSeverityVector
3.1[email protected]Secondary9.8CRITICALCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
3.1CNADECLARED9.8CRITICALCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

CVSS v3.1 Breakdown

Attack Vector
Network
Attack Complexity
Low
Privileges Required
None
User Interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
High

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

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA Fluent Fluentd affected < 1.19.3 Not specified

References

ReferenceSourceLinkTags
github.com/fluent/fluentd/releases/tag/v1.19.3 [email protected] github.com
github.com/fluent/fluentd/commit/45c87a81f3ac0b72b3f9dcfe8cfb5f9038f81437 [email protected] github.com
github.com/fluent/fluentd/security/advisories/GHSA-44hj-4m45-frj3 [email protected] github.com
github.com/fluent/fluentd/pull/5391 [email protected] github.com
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