Strix
64.7K

CVE-2026-59898

HIGHCVSS 7.5/10EPSS 0.27%

Last modified

CVE-2026-59898 is a high-severity vulnerability rated 7.5/10 on the CVSS scale. 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. EPSS estimates a 0.27% chance of exploitation in the next 30 days.

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.

Metrics

CVSS 3.1
7.5/10

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N

CVSS 4.0
6.3/10

CVSS:4.0/AV:N/AC:H/AT:N/PR:N/UI:N/VC:N/VI:N/VA:N/SC:L/SI:L/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X

EPSS Probability
0.27%

18.3th percentile

Probability of exploitation in the next 30 days. Learn more

Weakness Enumeration

Affected Software

VendorProductVersions
NettyNetty< 4.1.136
NettyNetty>= 4.2.0, < 4.2.16

References

Timeline

Published
Last Modified
Status
Analyzed

Frequently Asked Questions

What is CVE-2026-59898?
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.
How severe is CVE-2026-59898?
CVE-2026-59898 has a CVSS score of 7.5/10 (HIGH severity). The EPSS model estimates a 0.27% probability of exploitation in the next 30 days.
How do I fix CVE-2026-59898?
Check the vendor references and advisories linked above for patched versions and mitigation guidance. You can also run a Strix scan to test if your systems are affected.

How Strix Helps

Related CVEs from 2026

View all 2026CVEs →

Are you affected by CVE-2026-59898?

Run a free Strix scan to check your systems for this vulnerability.

Scan your code now

Source: NVD / NIST