# CVE-2026-89044: Other in netty

> Attackers can perform HTTP request smuggling by exploiting improper Transfer-Encoding validation in the Netty library, potentially bypassing security controls.

- **Severity:** Medium 6.9 (`CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:L/VI:L/VA:N/SC:N/SI:N/SA:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 10 Sep 2026
- **Updated:** 18 Sep 2026
- **Also known as:** CLEANSTART-2026-DD54267, CLEANSTART-2026-HA92776, CLEANSTART-2026-JI34331, CLEANSTART-2026-JM40588, CLEANSTART-2026-KP79659, CLEANSTART-2026-OZ38695, CLEANSTART-2026-TF82501, DEBIAN-CVE-2026-89044, GHSA-77qf-r755-9gcw, GHSA-hcvj-94mj-jp5c, UBUNTU-CVE-2026-89044

## What is CVE-2026-89044?

CVE-2026-89044 is a medium-severity vulnerability in Netty Netty, published on 10 Sep 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

Netty versions 4.1.133.Final through 4.1.137.Final and 4.2.13.Final through 4.2.17.Final fail to properly validate the final transfer coding in the Transfer-Encoding header, allowing attackers to smuggle requests by using malformed encoding declarations. Attackers can split Transfer-Encoding headers across multiple lines or use values like 'chunked, xchunked' to bypass validation and decode messages as chunked when the final coding is not chunked, enabling request smuggling attacks.

Weakness: CWE-444 (Inconsistent Interpretation of HTTP Requests)

## Which versions are affected by CVE-2026-89044?

It affects 1 product.


Products: Netty Netty.

## How do I fix CVE-2026-89044?

Upgrade to a fixed version.

## Is CVE-2026-89044 being exploited?

There is no known exploitation of CVE-2026-89044 in the wild and no public exploit code.

## Other vulnerabilities in Netty Netty

- [CVE-2026-75595](https://insights.sbomify.com/CVE-2026-75595/): Netty: SNI Routing Bypass via Fragmented TLS ClientHello Causing Fallback to Default SslContext (critical 9.1)
- [CVE-2026-75596](https://insights.sbomify.com/CVE-2026-75596/): Netty: Fragmented ClientHello records trigger quadratic pre-handshake reassembly in default SNI parsing (high 8.7)
- [CVE-2026-59901](https://insights.sbomify.com/CVE-2026-59901/): Netty Bzip2Decoder: Infinite Loop in RLE State Machine Leads to Event-Loop Thread Hang (high 8.7)
- [CVE-2026-55851](https://insights.sbomify.com/CVE-2026-55851/): Netty codec-haproxy: Signed-Byte Sentinel Collision in HAProxyMessageDecoder Leads to Unbounded Memory Exhaustion (high 8.7)
- [CVE-2026-56745](https://insights.sbomify.com/CVE-2026-56745/): Netty SpdyHttpDecoder: ByteBuf Reference Leak on RST_STREAM Leads to Native Memory Exhaustion (high 8.7)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-89044 and fix it if it is affected.

What it is: CVE-2026-89044 is a medium-severity vulnerability in Netty Netty, published on 10 Sep 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2026-89044 in the wild and no public exploit code.

Affected product: Netty Netty. No package-level version data is available, so check the vendor advisory linked from the reference page.

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-2026-89044/ (Markdown: https://insights.sbomify.com/CVE-2026-89044/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-89044
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-89044
- OSV: https://osv.dev/vulnerability/CVE-2026-89044

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-89044/
Summaries are generated and may contain mistakes; the official description above is the record.