CVE-2025-12978

CVE-2025-12978

MEDIUM
5.4
CVSS Score
Published: November 24, 2025 at 02:42 PM UTC
Updated: October 8, 2026 at 10:10 AM UTC
2 products affected across 2 vendorsFluent BitFluent Bit

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Severity
MEDIUM5.4
Exploit prediction
EPSS 0.4%
SSVC
No known exploit

Description

Fluent Bit in_http, in_splunk, and in_elasticsearch input plugins contain a flaw in the tag_key validation logic that fails to enforce exact key-length matching. This allows crafted inputs where a tag prefix is incorrectly treated as a full match. A remote attacker with authenticated or exposed access to these input endpoints can exploit this behavior to manipulate tags and redirect records to unintended destinations. This compromises the authenticity of ingested logs and can allow injection of forged data, alert flooding and routing manipulation.

Affected

Our own answer: ranges merged, affected separated from platform-only, with confidence and review flags.

v < 4.0.12
Affected range stops below 4.0.12, so it looks safe — our inference, not a vendor statement

Remediation

No guide yet

No remediation guidance has been written for this CVE yet, and no fixed version or vendor advisory is recorded against it.

References (1)

Release Notes
Source: cverecord
https://fluentbit.io/announcements/v4.1.0/

SSVC — Action Prioritization

SSVCNo known exploitNot automatablePartial impact

SSVC signals action urgency (what to patch first), separate from CVSS which measures severity.

CVSS

5.4MEDIUMCISA-ADP
Attack Vector
NETWORK
Complexity
LOW
Privileges
LOW
User Interaction
NONE
Scope
UNCHANGED
Confidentiality
NONE
Integrity
LOW
Availability
LOW
Vector?

Quick Info

StatusANALYZED
CWE
NVD-CWE-noinfo

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