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Vulnerabilities

Vulnerability · CVE-2025-12977

Fluent Bit in_http, in_splunk, and in_elasticsearch input plugins fail to sanitize tag_key inputs.

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-2025-12977. EPSS is 0.76%. 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
Critical9.1
Known exploitation
Not in CISA/VulnCheck KEV
EPSS
0.76%
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 fail to sanitize tag_key inputs. An attacker with network access or the ability to write records into Splunk or Elasticsearch can supply tag_key values containing special characters such as newlines or ../ that are treated as valid tags. Because tags influence routing and some outputs derive filenames or contents from tags, this can allow newline injection, path traversal, forged record injection, or log misrouting, impacting data integrity and log routing.

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-2025-12977

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-2025-12977. EPSS is 0.76%. 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 0.76%. 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 fail to sanitize tag_key inputs. An attacker with network access or the ability to write records into Splunk or Elasticsearch can supply tag_key values containing special characters such as newlines or ../ that are treated as valid tags. Because tags influence routing and some outputs derive filenames or contents from tags, this can

  2. Jan 7, 2026 · EUVD

    Updated

    Fluent Bit in_http, in_splunk, and in_elasticsearch input plugins fail to sanitize tag_key inputs. An attacker with network access or the ability to write records into Splunk or Elasticsearch can supply tag_key values containing special characters such as newlines or ../ that are treated as valid tags. Because tags influence routing and some outputs derive filenames or contents from tags, this can

Sources

  • CVE.orgVulnerability recordCVE-2025-12977

    Official CVE identifier

    cve.org
  • FIRST EPSSExploitation probabilityCVE-2025-12977

    30-day exploitation probability 0.76%

    first.org
  • EUVDVulnerability recordEUVD-2025-198811

    Fluent Bit in_http, in_splunk, and in_elasticsearch input plugins fail to sanitize tag_key inputs. An attacker with network access or the ability to write records into Splunk or Elasticsearch can supply tag_key values containing special characters such as newlines or ../ that are

    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