# CVE-2026-93574: Netty netty-codec-http request smuggling via chunk-size parsing

Source: https://junglewise.ai/threats/cve-2026-93574-a-flaw-was-found-in-netty-s-netty-codec-http-component-a-remote  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-09-18. Updated: 2026-09-26  
License: CC BY 4.0 with a link back

CVE-2026-93574 · Severity: medium · CVSS 6.5 · Published 2026-09-18

Netty is a popular networking library used in Java-based servers and proxies to handle HTTP communication. A flaw in its HTTP/1.1 chunk-size parsing allows an attacker to send malformed requests that bypass security controls in proxy deployments, potentially allowing unauthorized access to backend resources or cache poisoning attacks.

Technologies: [Netty Project Netty](https://junglewise.ai/threats/technologies/netty-project-netty). Vendors: [Netty Project](https://junglewise.ai/threats/vendors/netty-project).

## Quick answers

**Is CVE-2026-93574 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-93574 being exploited in the wild.

**How severe is CVE-2026-93574?** Medium severity, with a CVSS score of 6.5, published 18 September 2026.

**Which products and versions are affected?** Netty Project Netty <UNKNOWN>.

**Is there a fix for CVE-2026-93574?** No fixed version is recorded yet. Check the vendor's advisory in the references below. If you run it, Junglewise drafts a mitigation that fits your setup and applies it once you approve, with senior security engineers behind it.

**How is CVE-2026-93574 attacked?** It is attacked over the network, in a software library.

**Am I affected by CVE-2026-93574?** Check whether you run Netty Project Netty at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## Technical details

The vulnerability exists in netty-codec-http's chunk-size token parser, which incorrectly handles post-digit whitespace in HTTP/1.1 chunked transfer encoding headers. This parsing discrepancy enables HTTP request smuggling attacks where an attacker crafts a request that different entities (proxy vs backend) interpret differently. Remote, unauthenticated exploitation is possible over the network.

## Affected products

- Netty Project Netty <UNKNOWN>

## Timeline

- 2026-09-18: disclosed

## References

- [https://access.redhat.com/downloads/content/package-browser/](https://access.redhat.com/downloads/content/package-browser/)
- [https://access.redhat.com/jbossnetwork/restricted/listSoftware.html](https://access.redhat.com/jbossnetwork/restricted/listSoftware.html)

## Related threats

- [Netty incomplete hostname verification in QUIC certificate verification](https://junglewise.ai/threats/cve-2026-100665-netty-versions-from-4-2-11-final-before-4-2-18-final-contain-an)
- [Netty HTTP/2 header injection vulnerability](https://junglewise.ai/threats/cve-2026-93579-a-flaw-was-found-in-netty-s-http-2-stack-this-vulnerability)
- [Netty RedisArrayAggregator heap memory exhaustion](https://junglewise.ai/threats/cve-2026-93572-a-flaw-was-found-in-netty-s-redisarrayaggregator-component-a)
- [Netty SmtpResponseDecoder unbounded memory accumulation](https://junglewise.ai/threats/cve-2026-93563-a-flaw-was-found-in-netty-s-smtpresponsedecoder-component-a)
- [Netty memory leak in StompSubframeDecoder](https://junglewise.ai/threats/cve-2026-93494-a-flaw-was-found-in-netty-s-stompsubframedecoder-component-a)