What is CVE-2025-12978?

CVE-2025-12978 is a medium-severity vulnerability in Fluentbit Fluent Bit, classified under CWE-187: PARTIAL STRING COMPARISON. CVSS score: 5.4/10. Published 2025-11-24.

How severe is CVE-2025-12978?

Medium severity. CVSS v3 base score is 5.4 out of 10.

Vulnerability in Fluentbit Fluent Bit

CVE-2025-12978

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 ful…

EPSS: 0.003 (25.9th percentile) — read the EPSS interpretation.

CVSS v3 metric

CVSS v3 base score 5.4 (Medium). Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:L/A:L.

Affected products

Fluentbit Fluent Bit — versions 0
Treasuredata Fluent_bit — versions 4.1.0

References

cret@cert.org (Release Notes)

Frequently asked questions

What is CVE-2025-12978?: CVE-2025-12978 is a medium-severity vulnerability in Fluentbit Fluent Bit, classified under CWE-187: PARTIAL STRING COMPARISON. CVSS score: 5.4/10. Published 2025-11-24.
How severe is CVE-2025-12978?: Medium severity. CVSS v3 base score is 5.4 out of 10.