CVE-2026-59898

Netty: WebSockets V07/V08 handshaker missing Connection/Upgrade validation

HIGH

7.5

CVSS Score

Published: July 29, 2026 at 06:02 PM UTC

Updated: August 6, 2026 at 08:50 PM UTC

1 product affected across 1 vendorNetty

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Severity

HIGH7.5

Exploit prediction

EPSS 0.4%

SSVC

No known exploit

Description

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.

Affected

Our own answer: ranges merged, affected separated from platform-only, with confidence and review flags.

Netty · Nettymaven

95%

v < 4.1.136v < 4.1.136.Finalv < 4.2.16.Final4.2.0 ≤ v < 4.2.16

Affected range stops below 4.1.136, so it looks safe — our inference, not a vendor statement

Affected range stops below 4.1.136.Final, so it looks safe — our inference, not a vendor statement

Affected range stops below 4.2.16, so it looks safe — our inference, not a vendor statement

Affected range stops below 4.2.16.Final, so it looks safe — our inference, not a vendor statement

Remediation

No guide yet

No remediation guidance has been written for this CVE yet. What the record does show:

Patch and advisory references

https://github.com/netty/netty/security/advisories/GHSA-4mp9-239f-g9hg

References (3)

x_refsource_CONFIRMVendor Advisory

Source: cverecord

https://github.com/netty/netty/security/advisories/GHSA-4mp9-239f-g9hg

x_refsource_MISCRelease Notes

Source: cverecord

https://github.com/netty/netty/releases/tag/netty-4.1.136.Final

x_refsource_MISCRelease Notes

Source: cverecord

https://github.com/netty/netty/releases/tag/netty-4.2.16.Final

SSVC — Action Prioritization

SSVCNo known exploitNot automatablePartial impact

SSVC signals action urgency (what to patch first), separate from CVSS which measures severity.

CVSS

7.5HIGH[email protected]

Attack Vector: NETWORK
Complexity: LOW
Privileges: NONE
User Interaction: NONE
Scope: UNCHANGED
Confidentiality: NONE
Integrity: HIGH
Availability: NONE

Vector?

Quick Info

StatusANALYZED

CWE

CWE-444

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