ZDF
Sign inSign up

Vulnerabilities

Vulnerability · 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.

Published Nov 24, 2025 · catalog updated Jan 7, 2026 · FluentBit Fluent Bit

Last checked Oct 30, 2026. A connected source was read within the last 7 days.

Check if you run it

No confirmed exploitation is on record for CVE-2025-12978. EPSS is 0.41%. Act only if a listed version of FluentBit Fluent Bit is installed.

Gaps on this record

  • No vendor fix or required action is stored. Compare the linked advisory before you change production.

Same product and reporting

Severity
Medium5.4
Known exploitation
Not in CISA/VulnCheck KEV
EPSS
0.41%
Remediation
Version ranges on file
Affected products
vendor FluentBit Fluent Bit 0 <4.0.12

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.

Are you affected?

Enter the version you run. The result uses only the ranges stored on this record.

The check returns affected, not affected, or incomplete. It does not guess a version that is missing from the record.

  • vendor FluentBit Fluent Bit 0 <4.0.120 <4.0.12

How to fix CVE-2025-12978

What to do

Three questions, each answered from this record only. Confirm the vendor advisory before you patch.

Should you patch?

No confirmed exploitation is on record for CVE-2025-12978. EPSS is 0.41%. Act only if a listed version of FluentBit Fluent Bit is installed.

Which versions are affected?

Compare what you have installed with FluentBit Fluent Bit 0 <4.0.12 0 <4.0.12. Compare the installed version with the linked vendor advisory before you change production.

What should an analyst verify?

No weakness class is stored. EPSS 0.41%. There is no CISA KEV listing. No Exploit-DB or Metasploit reference is linked. Use the source links for the original advisory.

Technology hubs

Elasticsearch security

Code

The project this record applies to. Exploit listings stay in References.

No public source repository is identified for this product.

Timeline

Detection, updates, and resolution for this record.

  1. Nov 24, 2025 · EUVD

    Detected

    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 uni

  2. Jan 7, 2026 · EUVD

    Updated

    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 uni

Sources

  • CVE.orgVulnerability recordCVE-2025-12978

    Official CVE identifier

    cve.org
  • FIRST EPSSExploitation probabilityCVE-2025-12978

    30-day exploitation probability 0.41%

    first.org
  • EUVDVulnerability recordEUVD-2025-198807

    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 authentic

    euvd.enisa.europa.eu

References

Freshness

Last verified in this catalog Oct 30, 2026. Significant claims (KEV, EPSS, CVSS, affected ranges) come from the source rows above — open the original publisher for the authoritative advisory.

  • FIRST EPSSOct 30, 2026
  • CVE.orgOct 27, 2026
  • EUVDOct 27, 2026