Input Plugin Vulnerability in Fluent Bit Affects Data Integrity and Log Routing
CVE-2025-12977

9.1CRITICAL

Key Information:

Vendor

Fluentbit

Status
Fluent Bit
Vendor
CVE Published:
24 November 2025

Badges

👾 Exploit Exists📰 News Worthy

What is CVE-2025-12977?

Fluent Bit's in_http, in_splunk, and in_elasticsearch input plugins are vulnerable due to inadequate sanitization of tag_key inputs. An attacker capable of network access or manipulating records in Splunk or Elasticsearch can introduce tag_key values with special characters, such as newlines or directory traversal sequences (../). This manipulation can lead to serious consequences, including newline injection, path traversal, and forged record injection. The improper handling of tags can ultimately compromise the integrity of data and misroute log outputs, highlighting a critical area of concern for organizations relying on Fluent Bit for log management.

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Affected Version(s)

Fluent Bit 0 < 4.0.12

News Articles

favicon imagetheregister.com

Years-old bugs in open source took out major clouds at risk

A series of "trivial-to-exploit" vulnerabilities in Fluent Bit, an open source log collection tool that runs in every major cloud and AI lab, was left open for years, giving attackers an exploit chain to...

References

https://fluentbit.io/blog/2025/10/28/security-vulnerabili...
https://www.oligo.security/blog/critical-vulnerabilities-...

CVSS V3.1

Score:
9.1
Severity:
CRITICAL
Confidentiality:
High
Integrity:
High
Availability:
High
Attack Vector:
Network
Attack Complexity:
Low
Privileges Required:
None
User Interaction:
None
Scope:
Unchanged

Timeline

  • 👾

    Exploit known to exist

  • 📰

    First article discovered by theregister.com

  • Vulnerability published

  • Vulnerability Reserved

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