CVE-2026-59898: Netty: WebSockets V07/V08 handshaker missing Connection/Upgrade validation

Published Jul 22, 2026
·
Updated

Summary An attacker can force WebSocket upgrade via the lax V07 (or V08) handshaker by sending Sec-WebSocket-Version: 7 and omitting Connection: Upgrade / Upgrade: websocket headers, completing a protocol switch that a proxy would not recognize as an Upgrade request and enabling HTTP request smuggling / protocol-confusion attacks.

Other sources

Netty is an asynchronous, event-driven network application framework. Prior to versions 4.1.136.Final and 4.2.16.Final, ab attacker can force WebSocket upgrade via the lax V07 (or V08) handshaker by sending Sec-WebSocket-Version: 7 and omitting Connection: Upgrade / Upgrade: websocket headers, completing a protocol switch that a proxy would not recognize as an Upgrade request and enabling HTTP request smuggling / protocol-confusion attacks. This issue has been fixed in versions 4.1.136.Final and 4.2.16.Final.

— MITRE

Affected Software

4 affected componentsFixes available
maven/io.netty:netty-codec-http<4.1.136.Final
4.1.136.Final
maven/io.netty:netty-codec-http>=4.2.0.Final<=4.2.15.Final
4.2.16.Final
Netty Netty<4.1.136
Netty Netty>=4.2.0<4.2.16

Remediation

Recommended actions to resolve this vulnerability, in priority order.

  1. Upgrade

    Upgrade maven/io.netty:netty-codec-http to a version that resolves this vulnerability.

    Fixed in 4.1.136.Final
  2. Upgrade

    Upgrade maven/io.netty:netty-codec-http to a version that resolves this vulnerability.

    Fixed in 4.2.16.Final
  3. Upgrade

    Upgrade netty to a version that resolves this vulnerability.

    Fixed in 4.1.136.Final
  4. Upgrade

    Upgrade netty to a version that resolves this vulnerability.

    Fixed in 4.2.16.Final

Event History

Jul 22, 2026
Advisory Published
via GitHub·09:48 PM
Data Sourced
via GitHub·09:48 PM
DescriptionWeaknessAffected Software
Jul 29, 2026
CVE Published
via MITRE·06:02 PM
Data Sourced
via MITRE·06:02 PM
DescriptionWeakness
Data Sourced
via NVD·07:16 PM
DescriptionSeverityWeaknessAffected Software
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Frequently Asked Questions

1

What is the severity of CVE-2026-59898?

CVE-2026-59898 has a severity rating of 65.

2

How do I fix CVE-2026-59898?

To fix CVE-2026-59898, upgrade to a patched version of netty, specifically versions 4.1.136.Final or 4.2.16.Final.

3

What type of attack does CVE-2026-59898 facilitate?

CVE-2026-59898 facilitates unauthorized WebSocket upgrades by manipulating HTTP headers.

4

Which software is affected by CVE-2026-59898?

CVE-2026-59898 affects the maven/io.netty:netty-codec-http software.

5

When was CVE-2026-59898 published?

CVE-2026-59898 was published on July 22, 2026.

Company

Resources

Contact

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