VulnerabilityAnalyzed

CVE-2025-12978

This allows crafted inputs where a tag prefix is incorrectly treated as a full match.

MEDIUM 5.4EPSS 0.39%

Does this matter?

Lower severity and a low EPSS score (0.39%). Track it; it rarely justifies an emergency change on its own.

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.

CVSS 3.1: 5.4 MEDIUMCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:L/A:L
EPSS: 0.39% probability · 33th percentile
CISA KEV: Not listed
Affected: treasuredata/fluent bit
Source: cret@cert.org

References

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

Source: NVD record, EPSS from FIRST.org, KEV from CISA. Refreshed daily.