How severe is CVE-2026-42585?

CVE-2026-42585 has a CVSS score of 6.5/10, rated MEDIUM. Review your exposure and patch according to your risk tolerance.

Which packages are affected by CVE-2026-42585?

CVE-2026-42585 affects the following packages: io.netty:netty-codec-http (Maven), io.netty:netty-codec-http (Maven). Ecosystems affected: Maven.

How do I fix CVE-2026-42585?

Update io.netty:netty-codec-http to 4.2.13.Final or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-42585 is resolved across your whole dependency graph.

How do I detect CVE-2026-42585 in my Maven dependencies?

Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for io.netty:netty-codec-http. O3's reachability analysis confirms whether the vulnerable code path is actually invoked in your application, so you act on real exposure instead of every transitive match.

How do I mitigate CVE-2026-42585 if there is no patch (or I can't update yet)?

If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.

How does O3 Security protect against CVE-2026-42585?

O3 pinpoints whether CVE-2026-42585 is reachable in your code and exactly where to fix it, then blocks exploitation in production at runtime until the patched version is deployed.

Is CVE-2026-42585 actively exploited in the wild?

No public exploit code has been indexed for CVE-2026-42585 yet. This does not mean the vulnerability cannot be exploited — absence of public exploits does not imply safety. Apply the recommended fix and use O3 Security to monitor your exposure.

When was CVE-2026-42585 published, and has it been updated?

CVE-2026-42585 was published on May 13, 2026 and was last updated on July 15, 2026. Advisory data evolves as severity scores, affected ranges, and exploit intelligence are revised — always check the latest version of the advisory before acting.

☕ Maven

CVE-2026-42585

MEDIUM

CVE-2026-42585 is a medium-severity (CVSS 6.5) vulnerability in io.netty:netty-codec-http. O3 Security confirms whether CVE-2026-42585 is actually reachable in your code before you act, and blocks exploitation at runtime until you patch.

Netty: HTTP Request Smuggling due to malformed Transfer-Encoding

Also known asGHSA-38f8-5428-x5cv

Published

May 13, 2026

Updated

Jul 15, 2026

Affected

2 pkgs

Patched

2 / 2

Exploits

None indexed

Blast Radius

2 pkgs affected

☕io.netty:netty-codec-http☕io.netty:netty-codec-http

Real-time download stats are indexed for npm and PyPI packages. This vulnerability affects Maven packages — download data is not available via public APIs for these ecosystems.

Description

Netty is an asynchronous, event-driven network application framework. Prior to 4.2.13.Final and 4.1.133.Final, Netty incorrectly parses malformed Transfer-Encoding, enabling request smuggling attacks. This vulnerability is fixed in 4.2.13.Final and 4.1.133.Final.

Affected Packages

2 total 2 fixed

Ecosystem	Package	Vulnerable range	Fix
☕Maven	`io.netty:netty-codec-http`	≥ 4.2.0.Alpha1&&< 4.2.13.Final	4.2.13.Final
☕Maven	`io.netty:netty-codec-http`	all versions	4.1.133.Final

Detection & mitigation playbook

Open-source dependency

Detect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for io.netty:netty-codec-http. O3's reachability analysis confirms whether the vulnerable code path is actually invoked in your application, so you act on real exposure instead of every transitive match.
Fix
Update io.netty:netty-codec-http to 4.2.13.Final or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-42585 is resolved across your whole dependency graph.
Workarounds
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.
How O3 protects you
O3 pinpoints whether CVE-2026-42585 is reachable in your code and exactly where to fix it, then blocks exploitation in production at runtime until the patched version is deployed.

Tailored to CVE-2026-42585. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.

Frequently Asked Questions

O3 Security · Impact-Aware SCA

Is CVE-2026-42585 in your dependencies?

O3 detects CVE-2026-42585 across Maven dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.

Scan my dependencies How O3 SCA works