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

unknownCVE-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.

Details

Source: NVD Recent CVEs (US · database · site)
Severity: unknown
Published: 2026-07-29
Last updated: 2026-07-30
Exploitation: Not in CISA KEV at last sync

Original advisory: https://nvd.nist.gov/vuln/detail/CVE-2026-59898

Exploitation outlook

EPSS (FIRST.org) estimates each CVE’s probability of exploitation in the next 30 days — here is the CSIRTS.com read on those numbers.

Low exploitation riskCVE-2026-598980.27% 30-day exploitation probability — currently an unlikely target, but scores change as exploit code circulates. Riskier than 18% of all scored CVEs.

Referenced CVEs

CVE	CSIRTS overview	External
CVE-2026-59898	coverage & exploitation status	NVD · CVE.org

Same CVEs, other sources

How other CERTs, PSIRTs and databases cover the vulnerabilities in this advisory.

Recent advisories for Netty is an

A cluster of recent advisories against the same product widens the attack surface — attackers routinely chain freshly published CVEs on one product, so review these together.

highGHSA-93wv-jw9v-4972: Netty: HTTP/2 decompression leaks ByteBuf reference count when the decompressor channel i…ghsa · 2026-07-31
medium[NEW] [medium] Netty: Multiple vulnerabilitiescert-bund · 2026-07-30
high[NEW] [high] Netty: Multiple vulnerabilitiescert-bund · 2026-07-30
high[UPDATE] [high] Netty: Multiple vulnerabilitiescert-bund · 2026-07-30
mediumCVE-2026-59920: Netty is an asynchronous, event-driven network application framework. In versions prior to 4.1…nvd · 2026-07-29
mediumCVE-2026-59919: Netty is an asynchronous, event-driven network application framework. In versions prior to 4.1…nvd · 2026-07-29