FluentBit 4.1.0 in_forward missing authentication

Summaryinfo

A vulnerability was found in FluentBit 4.1.0 and classified as critical. This impacts an unknown function of the component in_forward. Such manipulation leads to missing authentication. This vulnerability is documented as CVE-2025-12969. The attack can be executed remotely. There is not any exploit available.

Detailsinfo

A vulnerability was found in FluentBit 4.1.0. It has been rated as critical. Affected by this issue is an unknown code of the component in_forward. The manipulation with an unknown input leads to a missing authentication vulnerability. Using CWE to declare the problem leads to CWE-306. The product does not perform any authentication for functionality that requires a provable user identity or consumes a significant amount of resources. Impacted is confidentiality, integrity, and availability. CVE summarizes:

Fluent Bit in_forward input plugin does not properly enforce the security.users authentication mechanism under certain configuration conditions. This allows remote attackers with network access to the Fluent Bit instance exposing the forward input to send unauthenticated data. By bypassing authentication controls, attackers can inject forged log records, flood alerting systems, or manipulate routing decisions, compromising the authenticity and integrity of ingested logs.

The advisory is available at fluentbit.io. This vulnerability is handled as CVE-2025-12969 since 11/10/2025. The exploitation is known to be easy. The attack may be launched remotely. No form of authentication is required for exploitation. The technical details are unknown and an exploit is not available. The structure of the vulnerability defines a possible price range of USD $0-$5k at the moment (estimation calculated on 12/22/2025).

The vulnerability scanner Nessus provides a plugin with the ID 276933 (Fluent Bit < 4.0.12 / 4.1.x < 4.1.1 Multiple Vulnerabilities), which helps to determine the existence of the flaw in a target environment.

There is no information about possible countermeasures known. It may be suggested to replace the affected object with an alternative product.

The vulnerability is also documented in the databases at Tenable (276933) and EUVD (EUVD-2025-198808). If you want to get best quality of vulnerability data, you may have to visit VulDB.

Productinfo

Name

• FluentBit

Version

• 4.1.0

CPE 2.3info

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CPE 2.2info

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Entryinfo

If you want to get best quality of vulnerability data, you may have to visit VulDB.

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