# CVE-2025-12978: CVE-2025-12978

> Remote attackers can manipulate log tags in Fluent Bit input plugins to redirect records and inject forged data due to flawed key validation.

- **Severity:** Medium 5.4 (`CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:L/A:L`)
- **Exploited in the wild:** Not known
- **Login needed:** Any signed-in user
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 24 Nov 2025
- **Updated:** 7 Jan 2026
- **Also known as:** BIT-fluent-bit-2025-12978, GHSA-7qw4-6c7x-f3pj

## What is CVE-2025-12978?

CVE-2025-12978 is a medium-severity vulnerability in FluentBit Fluent Bit, published on 24 Nov 2025. Any signed-in user can exploit it over the network, with no action from the victim.

### Official description

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.

## Which versions are affected by CVE-2025-12978?

1 open source package ship an affected version, including fluent-bit. It affects 1 product.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `fluent-bit` | Bitnami | From 4.1.0 | 4.1.1 |

Products: Treasuredata Fluent Bit.

## How do I fix CVE-2025-12978?

Upgrade fluent-bit to 4.1.1 or later.

## Is CVE-2025-12978 being exploited?

There is no known exploitation of CVE-2025-12978 in the wild and no public exploit code.

## Other vulnerabilities in FluentBit Fluent Bit

- [CVE-2024-4323](https://insights.sbomify.com/CVE-2024-4323/): Fluent Bit Memory Corruption Vulnerability (critical 9.8)
- [CVE-2021-36088](https://insights.sbomify.com/CVE-2021-36088/): Use after free in n/a (critical 9.8)
- [CVE-2025-12977](https://insights.sbomify.com/CVE-2025-12977/): CVE-2025-12977 (critical 9.1)
- [CVE-2025-12970](https://insights.sbomify.com/CVE-2025-12970/): CVE-2025-12970 (high 8.8)
- [CVE-2021-46878](https://insights.sbomify.com/CVE-2021-46878/): Use after free in n/a (high 7.8)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2025-12978 and fix it if it is affected.

What it is: CVE-2025-12978 is a medium-severity vulnerability in FluentBit Fluent Bit, published on 24 Nov 2025. Any signed-in user can exploit it over the network, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2025-12978 in the wild and no public exploit code.

Affected packages and fixed versions:
- fluent-bit (Bitnami): affected from 4.1.0; fixed in 4.1.1

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2025-12978/ (Markdown: https://insights.sbomify.com/CVE-2025-12978/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2025-12978
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2025-12978
- OSV: https://osv.dev/vulnerability/CVE-2025-12978

---
From sbomify Insights: https://insights.sbomify.com/CVE-2025-12978/
Summaries are generated and may contain mistakes; the official description above is the record.