# CVE-2026-44894: Netty's Default QUIC token handler accepts any client-supplied token

> Attackers can bypass QUIC address validation and amplification limits by sending spoofed tokens, enabling reflection attacks against victims.

- **Severity:** High 7.5 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 12 Jun 2026
- **Updated:** 15 Jul 2026
- **Also known as:** CLEANSTART-2026-HY47221, CLEANSTART-2026-PB26228, CLEANSTART-2026-SA68022, DEBIAN-CVE-2026-44894, ECHO-148d-a3b0-59be, GHSA-cmm3-54f8-px4j, MINI-46jj-3wf7-67hh, MINI-5gm9-gr69-38mq, MINI-8gc4-x63r-vpmp, MINI-95pp-gm35-vrgq, MINI-jpq3-rmq9-94p5, MINI-jqwm-vf7v-g89f, MINI-m8hw-p342-xch8, MINI-qwxg-8rp8-qrgg, MINI-vhhg-mpw8-fq5j, UBUNTU-CVE-2026-44894

## What is CVE-2026-44894?

CVE-2026-44894 is a high-severity vulnerability in Netty Netty, published on 12 Jun 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

Netty is a network application framework for development of protocol servers and clients. NoQuicTokenHandler is the tokenHandler used when the application does not set one. Prior to version 4.2.15.Final, its writeToken() returns false (server will not send Retry — acceptable), but validateToken() unconditionally `return 0`. In QuicheQuicServerCodec.handlePacket(), a non-negative return from validateToken() is interpreted as 'token is valid, ODCID starts at offset 0', causing the server to call quiche_accept as if the client's address had been validated by a Retry round-trip. Per RFC 9000 §8.1, a validated address lifts the 3× anti-amplification send limit. Thus any attacker who includes ANY non-empty token bytes in an Initial packet — with a spoofed victim source IP — causes the Netty server to treat the victim as validated and reflect full-size handshake flights (certificates, etc.) toward it without the 3× cap. The correct 'no token handler' semantics would be to return -1 (invalid) so the normal un-validated path and amplification limit apply. Version 4.2.15.Final patches the issue.

Weakness: CWE-346 (Origin Validation Error), CWE-940 (Improper Verification of Source of a Communication Channel)

## Which versions are affected by CVE-2026-44894?

2 open source packages ship an affected version, including io.netty:netty-codec-classes-quic. It affects 1 product.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `io.netty:netty-codec-classes-quic` | Maven | From 4.2.0.Final | 4.2.15.Final |
| `io.netty:netty-codec-classes-quic` | Maven | From 4.2.0.Final | 4.2.15.Final |

Products: Netty Netty.

## How do I fix CVE-2026-44894?

Upgrade io.netty:netty-codec-classes-quic to 4.2.15.Final or later.

## Is CVE-2026-44894 being exploited?

There is no known exploitation of CVE-2026-44894 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-2026-44894 and fix it if it is affected.

What it is: CVE-2026-44894 is a high-severity vulnerability in Netty Netty, published on 12 Jun 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-2026-44894 in the wild and no public exploit code.

Affected packages and fixed versions:
- io.netty:netty-codec-classes-quic (Maven): affected from 4.2.0.Final; fixed in 4.2.15.Final
- io.netty:netty-codec-classes-quic (Maven): affected from 4.2.0.Final; fixed in 4.2.15.Final

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-2026-44894/ (Markdown: https://insights.sbomify.com/CVE-2026-44894/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-44894
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-44894
- OSV: https://osv.dev/vulnerability/CVE-2026-44894

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-44894/
Summaries are generated and may contain mistakes; the official description above is the record.