CVE-2026-59898CWE-444

CVE-2026-59898

High · published July 29, 2026

CVSS v3.1
7.5
EPSS
0%
Percentile
37.1
In the wild
Unconfirmed
What it is

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.

The record
Technical detail
CVSS v3.1
7.5 · HIGH
Vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N
CVSS v4.0
Not supplied
EPSS
0.00439 · 37.1th percentile
Weakness
CWE-444 · Inconsistent Interpretation of HTTP Requests ('HTTP Request/Response Smuggling')
Published
2026-07-29T23:16Z
Affected products (2)
ProductVersionsFixed in
netty/netty< 4.1.1364.1.136
netty/netty≥ 4.2.0, < 4.2.164.2.16
References (3)
https://github.com/netty/netty/releases/tag/netty-4.1.136.Final · [email protected]https://github.com/netty/netty/releases/tag/netty-4.2.16.Final · [email protected]https://github.com/netty/netty/security/advisories/GHSA-4mp9-239f-g9hg · [email protected]
EPSS history
Timeline
  • 29 JUL 18:02Z
    Netty: WebSockets V07/V08 handshaker missing Connection/Upgrade validation
    cvelistv5